<figure><img src="image_226.png" /><figcaption>**Figure 18.** TEM images (left) of a) RhNPs and b) Hg particles and the corresponding size distributions (right) RhNPs ($d_m$ = 2.7 ± 0.1 nm; left) and Hg particles ($d_m$ = 16 ± 5 nm; right) in RhNP-TPPO@CCM-C.</figcaption></figure>

## Hydrogenation of other substrates

Lastly, the applicability of the RhNP-TPPO@CCM-C latex synthesized without base was screened for the aqueous biphasic hydrogenation of other substrates, including selected aromatics, alkenes, alkynes and carbonyl compounds (substrate/Rh = 5000/1; performed with neat substrate and not optimized) (Table 4). The results confirmed a rather high hydrogenation activity (average TOFs of 1000-1100 h⁻¹) and high selectivity towards the reduction of both double and triple carbon-carbon bonds in phenylacetylene (Entry 1) and 4-vinylpyridine (Entry 3). The catalytic activity was, however, significantly lower than for styrene under similar reaction conditions (cTOF 4500 h⁻¹; see Table 4). Highly sterically hindered Z-stilbene (Entry 2) and the aliphatic α,β-unsaturated substrate (E)-hex-2-enal (Entry 5) were only hydrogenated to a low extent under the applied conditions. Also, the carbonyl group of the aliphatic compound 5-nonanone (Entry 4) was hardly hydrogenated, whereas the cyclic (and activated) α,β-unsaturated substrate 2-cyclohexen-1-one (Entry 6) yielded a good conversion (cTOF of 1000 h⁻¹) with high selectivity (63.7%) to cyclohexanol, and acetophenone (Entry 7) showed an even higher conversion (cTOF of 3000 h⁻¹), with a nearly quantitative selectivity toward phenylethanol (>99%). Notably, no significant hydrogenation of the aromatic ring was observed in any of the reactions. Overall, the non-optimized results obtained during the screening clearly indicate the potential of the RhNP-TPPO@CCM-C catalyst synthesized without base for the hydrogenation of other types of unsaturated substrates than styrene.
<table><caption>**Table 4.** Aqueous biphasic hydrogenation using Rh-TPPO@CCM-C.<sup>a</sup></caption><thead><tr><th>Entry</th><th>Substrate /<br>Conversion (%)<sup>b</sup></th><th>Products /<br>Selectivity (%)<sup>b</sup></th><th>Average<br>cTOF<br>(h<sup>-1</sup>)</th></tr></thead><tbody><tr><td>1</td><td>30</td><td>77.6 22.4 &lt;0.1</td><td>1100</td></tr><tr><td>2</td><td>&lt;0.1</td><td>nd nd nd</td><td>2.5</td></tr><tr><td>3</td><td>79</td><td>96.8 nd</td><td>3200</td></tr><tr><td>4</td><td>&lt;0.1</td><td>nd</td><td>2.5</td></tr><tr><td>5</td><td>&lt;0.1</td><td>nd nd</td><td>2.5</td></tr><tr><td>6</td><td>27</td><td>1.4 34.9 63.7</td><td>1000</td></tr><tr><td>7</td><td>86 &gt;99 &lt;0.1 &lt;0.1</td><td></td><td>3000</td></tr></tbody></table>

**Conclusion and perspectives**

The aim of this PhD project was to develop new methods for efficient confinement of metal nanoparticles (MNPs) in polymeric core-crosslinked micelle (CCM) nanoreactors, with both cationic and anionic shells, for application of the resulting MNP@CCMs latexes in aqueous biphasic hydrogenation. To this end, novel core-crosslinked micelles functionalized with triphenylphosphine oxide and a polycationic shell were developed by extension of a previously optimized RAFT polymerization approach.

<footnote><sup>a</sup>Reaction conditions: Substrate/Rh = 5000/1, 20 bar H<sub>2</sub>, 25 °C, 0.25 h, 1200 rpm. <sup>b</sup>Conversions and selectivities determined by GC-FID. Product identification confirmed by <sup>1</sup>H NMR (Entries 4 and 5) and GC-MS (Entry 3). nd = not detected.</footnote>
<table><caption>**Table 4.** Aqueous biphasic hydrogenation using Rh-TPPO@CCM-C.<sup>a</sup></caption><thead><tr><th>Entry</th><th>Substrate /<br>Conversion (%)<sup>b</sup></th><th>Products /<br>Selectivity (%)<sup>b</sup></th><th>Average<br>cTOF<br>(h<sup>-1</sup>)</th></tr></thead><tbody><tr><td>1</td><td>30</td><td>77.6</td><td>1100</td></tr><tr><td>2</td><td>&lt;0.1</td><td>nd</td><td>2.5</td></tr><tr><td>3</td><td>79</td><td>96.8</td><td>3200</td></tr><tr><td>4</td><td>&lt;0.1</td><td>nd</td><td>2.5</td></tr><tr><td>5</td><td>&lt;0.1</td><td>nd</td><td>2.5</td></tr><tr><td>6</td><td>27</td><td>1.4</td><td>1000</td></tr><tr><td>7</td><td>86</td><td>&gt;99</td><td>3000</td></tr></tbody></table>

**Conclusion and perspectives**

The aim of this PhD project was to develop new methods for efficient confinement of metal nanoparticles (MNPs) in polymeric core-crosslinked micelle (CCM) nanoreactors, with both cationic and anionic shells, for application of the resulting MNP@CCMs latexes in aqueous biphasic hydrogenation. To this end, novel core-crosslinked micelles functionalized with triphenylphosphine oxide and a polycationic shell were developed by extension of a previously optimized RAFT polymerization approach.

<footnote><sup>a</sup>Reaction conditions: Substrate/Rh = 5000/1, 20 bar H<sub>2</sub>, 25 °C, 0.25 h, 1200 rpm. <sup>b</sup>Conversions and selectivities determined by GC-FID. Product identification confirmed by ¹H NMR (Entries 4 and 5) and GC-MS (Entry 3). nd = not detected.</footnote>
The first attempt to produce RhNP-TPPO@CCM-C consisted in loading the TPPO@CCM-C micelles with [Rh(COD)(μ-Cl)]₂, in order to generate a core-anchored [RhCl(COD)(TPPO@CCM-C)] complex that could be reduced to RhNPs by H₂, following the same procedure as previously developed to get RhNPs embedded in TPP@CCM-C. This proved unsuccessful, indicating that the formation of a Rh¹-TPPO@CCM-C complex by cleavage of the di-μ-Cl-bridge moiety in [Rh(COD)(μ-Cl)]₂ was not favorable in the polymer core under the applied conditions. Given that, an alternative strategy involving *ex-situ* synthesis of RhNPs using TPP and pyridine as stabilizers, affording ultrasmall RhNPs, and their subsequent transfer to the TPPO@CCM-C nanoreactors was envisaged. This strategy allowed the successful transfer of the RhNPs to the TPPO-functionalized cores. Although the resulting RhNP-TPPO@CCM-C latex proved effective in the aqueous biphasic hydrogenation of styrene, with only 2% of catalyst leaching, a gradual extraction of the TPP and pyridine ligands used for the *ex-situ* RhNPs synthesis during the work-up between recycles, induced a steady decrease of the catalytic activity. Nevertheless, a stable catalyst phase was obtained after preliminary extensive washing and an initial reaction run, yielding a TOF of ~1025 h⁻¹ (cTOF ~1440 h⁻¹), over several recycles.

To improve the system, a new approach has been developed consisting of a one-pot synthesis of RhNP-TPPO@CCM-C catalyst, which does not require the use of additional stabilizers. The produced RhNPs were smaller in size (1.7± 0.2 nm) than their analogs synthesized under similar conditions in the presence of only TPPO as stabilizer (2.4 ± 0.2 nm). This difference underlines the positive confinement effect on the RhNPs size, which leads to smaller NPs. The new catalyst demonstrated very good catalytic activity (cTOFs of 4500-16000 h⁻¹) and full selectivity in the hydrogenation of neat styrene to ethylbenzene under mild conditions (20 bar H₂, 25-55 °C). The catalyst was also applicable for the hydrogenation of other unsaturated substrates under similar reaction conditions, including alkynes and carbonyl compounds, making the RhNP-TPPO@CCM-C latex highly attractive for aqueous biphasic catalysis including catalyst recycling. The overall obtained catalytic results with RhNP-TPPO@CCM-C showed that the nature of the core-functional ligands of the polymer micelles is a key parameter to improving the stability and the recycling of the catalytic latex.

## References

[1] R. L. Johnston, *Metal nanoparticles and nanoalloys*, in *Frontiers of Nanoscience* (R. L. Johnston and J. P. Wilcoxon, Editors), Elsevier Ltd: Oxford, UK, **2012**, 3, 1–42. ISBN 978-0-08-096357-0. DOI: **10.1016/B978-0-08-096357-0.00006-6**.

[2] T. Shen, S. Zhou, J. Ruan, X. Chen, X. Liu, X. Ge, C. Qian, *Adv. Colloid Interface Sci.* **2021**, 287, 102299. DOI: **10.1016/j.cis.2020.102299**.

[3] T. Kotre, M. T. Zarka, J. O. Krause, M. R. Buchmeiser, R. Weberskirch, O. Nuyken, *Macromol Symp.* **2004**, 217, 203–21. DOI: **10.1002/masy.200451316**.

[4] B. Cornils, W. A. Herrmann, C. H. Wong and H. W. Zanthoff (Editors), *Catalysis from A to Z : A Concise Encyclopedia*, 4th ed., Wiley-VCH: Weinheim, Germany, **2013**, ISBN 978-3-527-33307-3.

[5] P. Serp, K. Philippot (Editors), *Nanomaterials in Catalysis*, Wiley-VCH: Weinheim, Germany, **2012**. ISBN: **9783527656875**. DOI: **10.1002/9783527656875**.

[6] D. Astruc (Editor), *Nanoparticles and Catalysis*, Wiley-VCH: Weinheim, Germany, **2007**. ISBN: **9783527621323**. DOI: **10.1002/9783527621323**.

[7] B. Chaudret, K. Philippot, *Oil & Gas Sci. Techn. - Rev. IFP*, **2007**, 62, 799–817. DOI: **10.2516/ogst:2007062**.

[8] A. Roucoux, J. Schulz, H. Patin, *Chem. Rev.* **2002**, 102, 3757–3778. DOI: **10.1021/cr010350j**.

[9] D. Astruc, F. Lu, J. R. Aranzaes, *Angew. Chem. Int. Ed.*, **2005**, 44, 7852–7872. DOI: **10.1002/anie.200500766**.
The first attempt to produce RhNP-TPPO@CCM-C consisted in loading the TPPO@CCM-C micelles with [Rh(COD)(μ-Cl)]₂, in order to generate a core-anchored [RhCl(COD)(TPPO@CCM-C)] complex that could be reduced to RhNPs by H₂, following the same procedure as previously developed to get RhNPs embedded in TPP@CCM-C. This proved unsuccessful, indicating that the formation of a Rh¹-TPPO@CCM-C complex by cleavage of the di-μ-Cl-bridge moiety in [Rh(COD)(μ-Cl)]₂ was not favorable in the polymer core under the applied conditions. Given that, an alternative strategy involving *ex-situ* synthesis of RhNPs using TPP and pyridine as stabilizers, affording ultrasmall RhNPs, and their subsequent transfer to the TPPO@CCM-C nanoreactors was envisaged. This strategy allowed the successful transfer of the RhNPs to the TPPO-functionalized cores. Although the resulting RhNP-TPPO@CCM-C latex proved effective in the aqueous biphasic hydrogenation of styrene, with only 2% of catalyst leaching, a gradual extraction of the TPP and pyridine ligands used for the *ex-situ* RhNPs synthesis during the work-up between recycles, induced a steady decrease of the catalytic activity. Nevertheless, a stable catalyst phase was obtained after preliminary extensive washing and an initial reaction run, yielding a TOF of ~1025 h⁻¹ (cTOF ~1440 h⁻¹), over several recycles.

To improve the system, a new approach has been developed consisting of a one-pot synthesis of RhNP-TPPO@CCM-C catalyst, which does not require the use of additional stabilizers. The produced RhNPs were smaller in size (1.7± 0.2 nm) than their analogs synthesized under similar conditions in the presence of only TPPO as stabilizer (2.4 ± 0.2 nm). This difference underlines the positive confinement effect on the RhNPs size, which leads to smaller NPs. The new catalyst demonstrated very good catalytic activity (cTOFs of 4500-16000 h⁻¹) and full selectivity in the hydrogenation of neat styrene to ethylbenzene under mild conditions (20 bar H₂, 25-55 °C). The catalyst was also applicable for the hydrogenation of other unsaturated substrates under similar reaction conditions, including alkynes and carbonyl compounds, making the RhNP-TPPO@CCM-C latex highly attractive for aqueous biphasic catalysis including catalyst recycling. The overall obtained catalytic results with RhNP-TPPO@CCM-C showed that the nature of the core-functional ligands of the polymer micelles is a key parameter to improving the stability and the recycling of the catalytic latex.

## References

[1] R. L. Johnston, *Metal nanoparticles and nanoalloys*, in *Frontiers of Nanoscience* (R. L. Johnston and J. P. Wilcoxon, Editors), Elsevier Ltd: Oxford, UK, **2012**, 3, 1–42. ISBN 978-0-08-096357-0. DOI: **10.1016/B978-0-08-096357-0.00006-6**.

[2] T. Shen, S. Zhou, J. Ruan, X. Chen, X. Liu, X. Ge, C. Qian, *Adv. Colloid Interface Sci.* **2021**, *287*, 102299. DOI: **10.1016/j.cis.2020.102299**.

[3] T. Kotre, M. T. Zarka, J. O. Krause, M. R. Buchmeiser, R. Weberskirch, O. Nuyken, *Macromol Symp.* **2004**, *217*, 203–21. DOI: **10.1002/masy.200451316**.

[4] B. Cornils, W. A. Herrmann, C. H. Wong and H. W. Zanthoff (Editors), *Catalysis from A to Z : A Concise Encyclopedia*, 4th ed., Wiley-VCH: Weinheim, Germany, **2013**, ISBN 978-3-527-33307-3.

[5] P. Serp, K. Philippot (Editors), *Nanomaterials in Catalysis*, Wiley-VCH: Weinheim, Germany, **2012**. ISBN: 9783527656875. DOI: **10.1002/9783527656875**.

[6] D. Astruc (Editor), *Nanoparticles and Catalysis*, Wiley-VCH: Weinheim, Germany, **2007**. ISBN: 9783527621323. DOI: **10.1002/9783527621323**.

[7] B. Chaudret, K. Philippot, *Oil & Gas Sci. Techn. - Rev. IFP*, **2007**, *62*, 799–817. DOI: **10.2516/ogst:2007062**.

[8] A. Roucoux, J. Schulz, H. Patin, *Chem. Rev.* **2002**, *102*, 3757–3778. DOI: **10.1021/cr010350j**.

[9] D. Astruc, F. Lu, J. R. Aranzaes, *Angew. Chem. Int. Ed.*, **2005**, *44*, 7852–7872. DOI: **10.1002/anie.200500766**.
[10] C. Burda, X. Chen, R. Narayanan, M. A. El-Sayed, *Chem. Rev.*, **2005**, *105*, 1025-1102. DOI: **10.1021/cr030063a**.

[11] M. Guerrero, N. T. T. Chau, S. Noël, A. Denicourt-Nowicki, F. Hapiot, A. Roucoux, E. Monflier, K. Philippot, *Curr. Org. Chem.*, **2013**, *17*, 364-399. DOI: **10.2174/1385272811317040006**.

[12] J. L. Castelbou, E. Bresó-Femenia, P. Blondeau, B. Chaudret, S. Castillón, C. Claver, C. Godard, *ChemCatChem*, **2014**, *6*, 3160-3168. DOI: **10.1002/cctc.201402524**.

[13] E. Guyonnet Bilé, R. Sassine, A. Denicourt-Nowicki, F. Launay, A. Roucoux, *Dalton Trans.*, **2011**, *40*, 6524-6531. DOI: **10.1039/c0dt01763a**.

[14] E. Guyonnet Bilé, E. Cortelazzo-Polisini, A. Denicourt-Nowicki, R. Sassine, F. Launay, A. Roucoux, *ChemSusChem*, **2012**, *5*, 91-101. DOI: **10.1002/cssc.201100364**.

[15] E. Guyonnet-Bilé, A. Denicourt-Nowicki, R. Sassine, P. Beaunier, F. Launay, A. Roucoux, *ChemSusChem*, **2010**, *3*, 1276-1279. DOI: **10.1002/cssc.201000206**.

[16] A. Borsla, A. M. Wilhelm, H. Delmas, *Cat. Today*, **2001**, *66*, 389-395. DOI: **10.1016/S0920-5861(00)00635-0**.

[17] H. Mao, X. Liao, B. Shi, *Catal. Commun.*, **2011**, *16*, 210-214. DOI: **10.1016/j.catcom.2011.09.038**.

[18] C. Chaudhari, H. Imatome, Y. Nishida, K. Sato, K. Nagaoka, *Catal. Commun.*, **2019**, *126*, 55-60. DOI: **10.1016/j.catcom.2019.02.019**.

[19] H. Hirai, M. Ohtaki, M. Komiyama, *Chem. Lett.*, **1987**, *16*, 149-152. DOI: **10.1246/CL.1987.149**.

[20] J. L. Castelbou, A. Gual, E. Mercadé, C. Claver, C. Godard, *Catal. Sci. Technol.*, **2013**, *3*, 2828-2833. DOI: **10.1039/c3cy00388d**.

[21] C. Moreno-Marrodan, F. Liguori, E. Mercadé, C. Godard, C. Claver, P. Barbaro, *Catal. Sci. Technol.*, **2013**, *5*, 3762-3772. DOI: **10.1039/c5cy00599j**.

[22] F. Martinez-Espinar, P. Blondeau, P. Nolis, B. Chaudret, C. Claver, S. Castillón, C. Godard, *J. Catal.*, **2017**, *354*, 113-127. DOI: **10.1016/j.jcat.2017.08.010**.

[23] C. Amiens, D. Ciuculescu-Pradines, K. Philippot, *Coord. Chem. Rev.*, **2016**, *308*, 409-432. DOI: **10.1016/j.ccr.2015.07.013**.

[24] M. R. Axet, S. Castillón, C. Claver, K. Philippot, P. Lecante, B. Chaudret, *Eur. J. Inorg. Chem.*, **2008**, 3460-3466. DOI: **10.1002/ejic.200800421**.

[25] J. L. Pellegatta, C. Blandy, V. Collière, R. Choukroun, B. Chaudret, P. Cheng, K. Philippot, *J. Mol. Cat. A* **2002**, *178*, 55-61. DOI: **10.1016/s1381-1169(01)00298-9**.

[26] M. Ibrahim, M. Wei, É. Deydier, E. Manoury, R. Poli, P. Lecante, K. Philippot, *Dalton Trans.*, **2019**, *48*, 6777-6786. DOI: **10.1039/C9DT01006H**.

[27] D. V. Talapin, E. V. Shevchenko, *Chem. Rev.*, **2016**, *116*, 10343-10345. DOI: **10.1021/acs.chemrev.6b00566**.

[28] P. P. R. W. Oskar Nuyken, *Macromol. Symp.*, **2002**, *177*, 163-173. DOI: **10.1002/1521-3900(200201)177:1<163::AID-MASY163>3.0.CO;2-W**.

[29] M. Niyaz Khan, *Micellar Catalysis*; CRC Press: Boca Raton, **2006**, ISBN 9780429133749. DOI: **10.1201/9781420015843**.

[30] M. R. Buchmeiser (Editor), *Polymeric Materials in Organic Synthesis and Catalysis*, Wiley-VCH: Weinheim, Germany, **2003**, ISBN 3527305149. DOI: **10.1002/3527601856**.

[31] M. Schrinner, F. Polzer, Y. Mei, Y. Lu, B. Haupt, M. Ballauff, A. Göldel, M. Drechsler, J. Preussner, U. Glatzel, *Macromol. Chem. Phys.*, **2007**, *208*, 1542-1547. DOI: **10.1002/macp.200700161**.

[32] Y. Lu, Y. Mei, M. Schrinner, M. Ballauff, M. W. Möller, J. Breu, *J. Phys. Chem.*, **2007**, *111*, 7676-7681. DOI: **10.1021/jp070973m**.

[33] R. K. O'Reilly, C. J. Hawker, K. L. Wooley, *Chem. Soc. Rev.*, **2006**, *35*, 1068-1083. DOI: **10.1039/b514858h**.

[34] S. Chen, F. Gayet, E. Manoury, A. Joumaa, M. Lansalot, F. D'Agosto, R. Poli, *Chem. Eur. J.*, **2016**, *22*, 6302-6313. DOI: **10.1002/chem.201504923**.

[35] A. Joumaa, F. Gayet, E. J. Garcia-Suarez, J. Himmelstrup, A. Riisager, R. Poli, E. Manoury, *Polymers*, **2020**, *12*, 1107. DOI: **10.3390/POLYM12051107**.

[36] H. Wang, C. Fliedel, E. Manoury, R. Poli, *Polymer*, **2022**, *243*, 124640. DOI: **10.1016/j.polymer.2022.124640**.
[10] C. Burda, X. Chen, R. Narayanan, M. A. El-Sayed, *Chem. Rev.*, **2005**, *105*, 1025-1102. DOI: **10.1021/cr030063a**.

[11] M. Guerrero, N. T. T. Chau, S. Noël, A. Denicourt-Nowicki, F. Hapiot, A. Roucoux, E. Monflier, K. Philippot, *Curr. Org. Chem.*, **2013**, *17*, 364-399. DOI: **10.2174/1385272811317040006**.

[12] J. L. Castelbou, E. Bresó-Femenia, P. Blondeau, B. Chaudret, S. Castillón, C. Claver, C. Godard, *ChemCatChem*, **2014**, *6*, 3160-3168. DOI: **10.1002/cctc.201402524**.

[13] E. Guyonnet Bilé, R. Sassine, A. Denicourt-Nowicki, F. Launay, A. Roucoux, *Dalton Trans.*, **2011**, *40*, 6524-6531. DOI: **10.1039/c0dt01763a**.

[14] E. Guyonnet Bilé, E. Cortelazzo-Polisini, A. Denicourt-Nowicki, R. Sassine, F. Launay, A. Roucoux, *ChemSusChem*, **2012**, *5*, 91-101. DOI: **10.1002/cssc.201100364**.

[15] E. Guyonnet-Bilé, A. Denicourt-Nowicki, R. Sassine, P. Beaunier, F. Launay, A. Roucoux, *ChemSusChem*, **2010**, *3*, 1276-1279. DOI: **10.1002/cssc.201000206**.

[16] A. Borsla, A. M. Wilhelm, H. Delmas, *Cat. Today*, **2001**, *66*, 389-395. DOI: **10.1016/S0920-5861(00)00635-0**.

[17] H. Mao, X. Liao, B. Shi, *Catal. Commun.*, **2011**, *16*, 210-214. DOI: **10.1016/j.catcom.2011.09.038**.

[18] C. Chaudhari, H. Imatome, Y. Nishida, K. Sato, K. Nagaoka, *Catal. Commun.*, **2019**, *126*, 55-60. DOI: **10.1016/j.catcom.2019.02.019**.

[19] H. Hirai, M. Ohtaki, M. Komiyama, *Chem. Lett.*, **1987**, *16*, 149-152. DOI: **10.1246/CL.1987.149**.

[20] J. L. Castelbou, A. Gual, E. Mercadé, C. Claver, C. Godard, *Catal. Sci. Technol.*, **2013**, *3*, 2828-2833. DOI: **10.1039/c3cy00388d**.

[21] C. Moreno-Marrodan, F. Liguori, E. Mercadé, C. Godard, C. Claver, P. Barbaro, *Catal. Sci. Technol.*, **2013**, *5*, 3762-3772. DOI: **10.1039/c5cy00599j**.

[22] F. Martinez-Espinar, P. Blondeau, P. Nolis, B. Chaudret, C. Claver, S. Castillón, C. Godard, *J. Catal.*, **2017**, *354*, 113-127. DOI: **10.1016/j.jcat.2017.08.010**.

[23] C. Amiens, D. Ciuculescu-Pradines, K. Philippot, *Coord. Chem. Rev.*, **2016**, *308*, 409-432. DOI: **10.1016/j.ccr.2015.07.013**.

[24] M. R. Axet, S. Castillón, C. Claver, K. Philippot, P. Lecante, B. Chaudret, *Eur. J. Inorg. Chem.*, **2008**, 3460-3466. DOI: **10.1002/ejic.200800421**.

[25] J. L. Pellegatta, C. Blandy, V. Collière, R. Choukroun, B. Chaudret, P. Cheng, K. Philippot, *J. Mol. Cat. A* **2002**, *178*, 55-61. DOI: **10.1016/s1381-1169(01)00298-9**.

[26] M. Ibrahim, M. Wei, É. Deydier, E. Manoury, R. Poli, P. Lecante, K. Philippot, *Dalton Trans.*, **2019**, *48*, 6777-6786. DOI: **10.1039/C9DT01006H**.

[27] D. V. Talapin, E. V. Shevchenko, *Chem. Rev.*, **2016**, *116*, 10343-10345. DOI: **10.1021/acs.chemrev.6b00566**.

[28] P. P. R. W. Oskar Nuyken, *Macromol. Symp.*, **2002**, *177*, 163-173. DOI: **10.1002/1521-3900(200201)177:1<163::AID-MASY163>3.0.CO;2-W**.

[29] M. Niyaz Khan, *Micellar Catalysis*; CRC Press: Boca Raton, **2006**, ISBN 9780429133749. DOI: **10.1201/9781420015843**.

[30] M. R. Buchmeiser (Editor), *Polymeric Materials in Organic Synthesis and Catalysis*, Wiley-VCH: Weinheim, Germany, **2003**, ISBN 3527305149. DOI: **10.1002/3527601856**.

[31] M. Schrinner, F. Polzer, Y. Mei, Y. Lu, B. Haupt, M. Ballauff, A. Göldel, M. Drechsler, J. Preussner, U. Glatzel, *Macromol. Chem. Phys.*, **2007**, *208*, 1542-1547. DOI: **10.1002/macp.200700161**.

[32] Y. Lu, Y. Mei, M. Schrinner, M. Ballauff, M. W. Möller, J. Breu, *J. Phys. Chem.*, **2007**, *111*, 7676-7681. DOI: **10.1021/jp070973m**.

[33] R. K. O'Reilly, C. J. Hawker, K. L. Wooley, *Chem. Soc. Rev.*, **2006**, *35*, 1068-1083. DOI: **10.1039/b514858h**.

[34] S. Chen, F. Gayet, E. Manoury, A. Joumaa, M. Lansalot, F. D'Agosto, R. Poli, *Chem. Eur. J.*, **2016**, *22*, 6302-6313. DOI: **10.1002/chem.201504923**.

[35] A. Joumaa, F. Gayet, E. J. Garcia-Suarez, J. Himmelstrup, A. Riisager, R. Poli, E. Manoury, *Polymers*, **2020**, *12*, 1107. DOI: **10.3390/POLYM12051107**.

[36] H. Wang, C. Fliedel, E. Manoury, R. Poli, *Polymer*, **2022**, *243*, 124640. DOI: **10.1016/j.polymer.2022.124640**.
[37] H. Wang, L. Vendrame, C. Fliedel, S. Chen, F. Gayet, F. D'Agosto, M. Lansalot, E. Manoury, R. Poli, *Chem. Eur. J.*, **2021**, *27*, 5205–5214. DOI: [10.1002/chem.202004689](https://doi.org/10.1002/chem.202004689).

[38] H. Wang, L. Vendrame, C. Fliedel, S. Chen, F. Gayet, E. Manoury, X. Zhang, F. D'agosto, M. Lansalot, R. Poli, *Macromolecules*, **2020**, *53*, 2198–2208. DOI: [10.1021/acs.macromol.9b02582](https://doi.org/10.1021/acs.macromol.9b02582).

[39] S. S. Sambou, R. Hromov, I. Ruzhylo, H. Wang, A. Allandrieu, C. Sabatier, Y. Coppel, J. C. Daran, F. Gayet, A. Labande, E. Manoury, R. Poli, *Catal. Sci. Technol.*, **2021**, *11*, 6811–6824. DOI: [10.1039/d1cy00554e](https://doi.org/10.1039/d1cy00554e).

[40] H. Wang, A. M. Fiore, C. Fliedel, E. Manoury, K. Philippot, M. M. Dell'Anna, P. Mastrorilli, R. Poli, *Nanoscale Adv.* **2021**, *3*, 2554–2566. DOI: [10.1039/d1na00028d](https://doi.org/10.1039/d1na00028d).

[41] A. F. Cardozo, C. Julcour, L. Barthe, J. F. Blanco, S. Chen, F. Gayet, E. Manoury, X. Zhang, M. Lansalot, B. Charleux, F. D'Agosto, R. Poli, H. Delmas, *J. Catal.*, **2015**, *324*, 1–8. DOI: [10.1016/j.jcat.2015.01.009](https://doi.org/10.1016/j.jcat.2015.01.009).

[42] F. D'Agosto, J. Rieger, M. Lansalot, *Angew. Chem. Int. Ed.*, **2020**, *59*, 8368–8392. DOI: [10.1002/anie.201911758](https://doi.org/10.1002/anie.201911758).

[43] H. Wang, C. J. Abou-Fayssal, C. Fliedel, E. Manoury, R. Poli, *Polymers*, **2022**, *14*, 4937. DOI: [10.3390/polym14224937](https://doi.org/10.3390/polym14224937).

[44] E. Lobry, A. F. Cardozo, L. Barthe, J. F. Blanco, H. Delmas, S. Chen, F. Gayet, X. Zhang, M. Lansalot, F. D'Agosto, R. Poli, E. Manoury, C. Julcour, *J. Catal.*, **2016**, *342*, 164–172. DOI: [10.1016/j.jcat.2016.07.023](https://doi.org/10.1016/j.jcat.2016.07.023).

[45] S. Chen, A. F. Cardozo, C. Julcour, J. F. Blanco, L. Barthe, F. Gayet, M. Lansalot, F. D'Agosto, H. Delmas, E. Manoury, R. Poli, *Polymer*, **2015**, *72*, 327–335. DOI: [10.1016/j.polymer.2015.02.024](https://doi.org/10.1016/j.polymer.2015.02.024).

[46] R. El Abed, F. Aloui, J. P. Genêt, B. Ben Hassine, A. Marinetti, *J. Organomet. Chem.*, **2007**, *692*, 1156–1160. DOI: [10.1016/j.jorganchem.2006.11.022](https://doi.org/10.1016/j.jorganchem.2006.11.022).

[47] J. Sanmartín, M. R. Bermejo, C. A. McAuliffe, A. Sousa, M. Fondo, E. Gómez-Fórneas, *Inorg. Chim. Acta*, **1997**, *255*, 269–278. DOI: [10.1016/S0020-1693(96)05373-X](https://doi.org/10.1016/S0020-1693(96)05373-X).

[48] N. Suzuki, T. Inoue, T. Asada, R. Akebi, G. Kobayashi, M. Rikukawa, Y. Masuyama, M. Ogasawara, T. Takahashi, *Chem. Lett.*, **2013**, *42*, 1493–1495. DOI: [10.1246/cl.130711](https://doi.org/10.1246/cl.130711).

[49] C. Li, Y. Wang, D. Sun, H. Li, X. Sun, D. Ma, Z. Ren, S. Yan, *ACS Appl. Mater. Interfaces*, **2018**, *10*, 5731–5739. DOI: [10.1021/acsami.8b00136](https://doi.org/10.1021/acsami.8b00136).

[50] S. Vanicek, M. Podewitz, J. Stubbe, D. Schulze, H. Kopacka, K. Wurst, T. Müller, P. Lippmann, S. Haslinger, H. Schottenberger, K. R. Liedl, I. Ott, B. Sarkar, B. Bildstein, *Chem. Eur. J.*, **2018**, *24*, 3742–3753. DOI: [10.1002/chem.201705051](https://doi.org/10.1002/chem.201705051).

[51] M. Deimling, M. Kirchhof, B. Schwager, Y. Qawasmi, A. Savin, T. Mühlhäuser, W. Frey, B. Claasen, A. Baro, T. Sottmann, S. Laschat, *Chem. Eur. J.*, **2019**, *25*, 9464–9476. DOI: [10.1002/chem.201900947](https://doi.org/10.1002/chem.201900947).

[52] J. Nowakowski, S. Nowakowska, G. Srivastava, M. Baljozovic, J. Girovsky, N. Ballav, T. A. Jung, *ChemistrySelect*, **2016**, *1*, 891–895. DOI: [10.1002/slct.201600215](https://doi.org/10.1002/slct.201600215).

[53] T. Nishimura, Y. Maeda, T. Hayashi, *Angew. Chem. Int. Ed.*, **2010**, *49*, 7324–7327. DOI: [10.1002/anie.201003775](https://doi.org/10.1002/anie.201003775).

[54] F. H. Hu, L. S. Wang, S. F. Cai, *J. Chem. Eng. Data*, **2009**, *54*, 1382–1384. DOI: [10.1021/je800842z](https://doi.org/10.1021/je800842z).

[55] P. Das, P. Chutia, D. Kumar Dutta, *Chem. Lett.*, **2002**, *7*, 766–767. DOI: [10.1246/cl.2002.766](https://doi.org/10.1246/cl.2002.766).

[56] R. Bonnaire, D. Diavoust, N. Platzer, *Org. Mag. Reson.*, **1984**, *22*, 80–85. DOI: [10.1002/mrc.1270220205](https://doi.org/10.1002/mrc.1270220205).

[57] A. Serrano-Maldonado, E. Martin, I. Guerrero-Ríos, *Eur. J. Inorg. Chem.*, **2019**, 2863–2870. DOI: [10.1002/ejic.201900223](https://doi.org/10.1002/ejic.201900223).

[58] S. A. Stratton, K. L. Luska, A. Moores, *Catal Today.*, **2012**, *183*, 96–100. DOI: [10.1016/j.cattod.2011.09.016](https://doi.org/10.1016/j.cattod.2011.09.016).

[59] X. Zhang, A. F. Cardozo, S. Chen, W. Zhang, C. Julcour, M. Lansalot, J. F. Blanco, F. Gayet, H. Delmas, B. Charleux, E. Manoury, F. D'Agosto, R. Poli, *Chem. Eur. J.*, **2014**, *20*, 15505–15517. DOI: [10.1002/chem.201403819](https://doi.org/10.1002/chem.201403819).

[60] H. Ohde, M. Ohde, C. M. Wai, *Chem. Comm.*, **2004**, *4*, 930–931. DOI: [10.1039/b311522d](https://doi.org/10.1039/b311522d).

[61] M. L. Buil, M. A. Esteruelas, S. Niembro, M. Oliván, L. Orzechowski, C. Pelayo, A. Vallribera, *Organometallics*, **2010**, *29*, 4375–4383. DOI: [10.1021/om1003072](https://doi.org/10.1021/om1003072).

[62] J. Schulz, S. Levigne, A. Roucoux, H. Patin, *Adv. Synth. Catal.*, **2002**, *344*, 266–269. DOI: [10.1002/1615-4169(200206)344:3<266::AID-ADSC266>3.0.CO;2-O](https://doi.org/10.1002/1615-4169(200206)344:3<266::AID-ADSC266>3.0.CO;2-O).

[63] N. Yan, Y. Yuan, P. J. Dyson, *Chem. Comm.*, **2011**, *47*, 2529–2531. DOI: [10.1039/c0cc04641h](https://doi.org/10.1039/c0cc04641h).
[37] H. Wang, L. Vendrame, C. Fliedel, S. Chen, F. Gayet, F. D'Agosto, M. Lansalot, E. Manoury, R. Poli, *Chem. Eur. J.*, **2021**, *27*, 5205–5214. DOI: [10.1002/chem.202004689](https://doi.org/10.1002/chem.202004689).

[38] H. Wang, L. Vendrame, C. Fliedel, S. Chen, F. Gayet, E. Manoury, X. Zhang, F. D'agosto, M. Lansalot, R. Poli, *Macromolecules*, **2020**, *53*, 2198–2208. DOI: [10.1021/acs.macromol.9b02582](https://doi.org/10.1021/acs.macromol.9b02582).

[39] S. S. Sambou, R. Hromov, I. Ruzhylo, H. Wang, A. Allandrieu, C. Sabatier, Y. Coppel, J. C. Daran, F. Gayet, A. Labande, E. Manoury, R. Poli, *Catal. Sci. Technol.*, **2021**, *11*, 6811–6824. DOI: [10.1039/d1cy00554e](https://doi.org/10.1039/d1cy00554e).

[40] H. Wang, A. M. Fiore, C. Fliedel, E. Manoury, K. Philippot, M. M. Dell'Anna, P. Mastrorilli, R. Poli, *Nanoscale Adv.* **2021**, *3*, 2554–2566. DOI: [10.1039/d1na00028d](https://doi.org/10.1039/d1na00028d).

[41] A. F. Cardozo, C. Julcour, L. Barthe, J. F. Blanco, S. Chen, F. Gayet, E. Manoury, X. Zhang, M. Lansalot, B. Charleux, F. D'Agosto, R. Poli, H. Delmas, *J. Catal.*, **2015**, *324*, 1–8. DOI: [10.1016/j.jcat.2015.01.009](https://doi.org/10.1016/j.jcat.2015.01.009).

[42] F. D'Agosto, J. Rieger, M. Lansalot, *Angew. Chem. Int. Ed.*, **2020**, *59*, 8368–8392. DOI: [10.1002/anie.201911758](https://doi.org/10.1002/anie.201911758).

[43] H. Wang, C. J. Abou-Fayssal, C. Fliedel, E. Manoury, R. Poli, *Polymers*, **2022**, *14*, 4937. DOI: [10.3390/polym14224937](https://doi.org/10.3390/polym14224937).

[44] E. Lobry, A. F. Cardozo, L. Barthe, J. F. Blanco, H. Delmas, S. Chen, F. Gayet, X. Zhang, M. Lansalot, F. D'Agosto, R. Poli, E. Manoury, C. Julcour, *J. Catal.*, **2016**, *342*, 164–172. DOI: [10.1016/j.jcat.2016.07.023](https://doi.org/10.1016/j.jcat.2016.07.023).

[45] S. Chen, A. F. Cardozo, C. Julcour, J. F. Blanco, L. Barthe, F. Gayet, M. Lansalot, F. D'Agosto, H. Delmas, E. Manoury, R. Poli, *Polymer*, **2015**, *72*, 327–335. DOI: [10.1016/j.polymer.2015.02.024](https://doi.org/10.1016/j.polymer.2015.02.024).

[46] R. El Abed, F. Aloui, J. P. Genêt, B. Ben Hassine, A. Marinetti, *J. Organomet. Chem.*, **2007**, *692*, 1156–1160. DOI: [10.1016/j.jorganchem.2006.11.022](https://doi.org/10.1016/j.jorganchem.2006.11.022).

[47] J. Sanmartín, M. R. Bermejo, C. A. McAuliffe, A. Sousa, M. Fondo, E. Gómez-Fórneas, *Inorg. Chim. Acta*, **1997**, *255*, 269–278. DOI: [10.1016/S0020-1693(96)05373-X](https://doi.org/10.1016/S0020-1693(96)05373-X).

[48] N. Suzuki, T. Inoue, T. Asada, R. Akebi, G. Kobayashi, M. Rikukawa, Y. Masuyama, M. Ogasawara, T. Takahashi, *Chem. Lett.*, **2013**, *42*, 1493–1495. DOI: [10.1246/cl.130711](https://doi.org/10.1246/cl.130711).

[49] C. Li, Y. Wang, D. Sun, H. Li, X. Sun, D. Ma, Z. Ren, S. Yan, *ACS Appl. Mater. Interfaces*, **2018**, *10*, 5731–5739. DOI: [10.1021/acsami.8b00136](https://doi.org/10.1021/acsami.8b00136).

[50] S. Vanicek, M. Podewitz, J. Stubbe, D. Schulze, H. Kopacka, K. Wurst, T. Müller, P. Lippmann, S. Haslinger, H. Schottenberger, K. R. Liedl, I. Ott, B. Sarkar, B. Bildstein, *Chem. Eur. J.*, **2018**, *24*, 3742–3753. DOI: [10.1002/chem.201705051](https://doi.org/10.1002/chem.201705051).

[51] M. Deimling, M. Kirchhof, B. Schwager, Y. Qawasmi, A. Savin, T. Mühlhäuser, W. Frey, B. Claasen, A. Baro, T. Sottmann, S. Laschat, *Chem. Eur. J.*, **2019**, *25*, 9464–9476. DOI: [10.1002/chem.201900947](https://doi.org/10.1002/chem.201900947).

[52] J. Nowakowski, S. Nowakowska, G. Srivastava, M. Baljozovic, J. Girovsky, N. Ballav, T. A. Jung, *ChemistrySelect*, **2016**, *1*, 891–895. DOI: [10.1002/slct.201600215](https://doi.org/10.1002/slct.201600215).

[53] T. Nishimura, Y. Maeda, T. Hayashi, *Angew. Chem. Int. Ed.*, **2010**, *49*, 7324–7327. DOI: [10.1002/anie.201003775](https://doi.org/10.1002/anie.201003775).

[54] F. H. Hu, L. S. Wang, S. F. Cai, *J. Chem. Eng. Data*, **2009**, *54*, 1382–1384. DOI: [10.1021/je800842z](https://doi.org/10.1021/je800842z).

[55] P. Das, P. Chutia, D. Kumar Dutta, *Chem. Lett.*, **2002**, *7*, 766–767. DOI: [10.1246/cl.2002.766](https://doi.org/10.1246/cl.2002.766).

[56] R. Bonnaire, D. Diavoust, N. Platzer, *Org. Mag. Reson.*, **1984**, *22*, 80–85. DOI: [10.1002/mrc.1270220205](https://doi.org/10.1002/mrc.1270220205).

[57] A. Serrano-Maldonado, E. Martin, I. Guerrero-Ríos, *Eur. J. Inorg. Chem.*, **2019**, 2863–2870. DOI: [10.1002/ejic.201900223](https://doi.org/10.1002/ejic.201900223).

[58] S. A. Stratton, K. L. Luska, A. Moores, *Catal Today.*, **2012**, *183*, 96–100. DOI: [10.1016/j.cattod.2011.09.016](https://doi.org/10.1016/j.cattod.2011.09.016).

[59] X. Zhang, A. F. Cardozo, S. Chen, W. Zhang, C. Julcour, M. Lansalot, J. F. Blanco, F. Gayet, H. Delmas, B. Charleux, E. Manoury, F. D'Agosto, R. Poli, *Chem. Eur. J.*, **2014**, *20*, 15505–15517. DOI: [10.1002/chem.201403819](https://doi.org/10.1002/chem.201403819).

[60] H. Ohde, M. Ohde, C. M. Wai, *Chem. Comm.*, **2004**, *4*, 930–931. DOI: [10.1039/b311522d](https://doi.org/10.1039/b311522d).

[61] M. L. Buil, M. A. Esteruelas, S. Niembro, M. Oliván, L. Orzechowski, C. Pelayo, A. Vallribera, *Organometallics*, **2010**, *29*, 4375–4383. DOI: [10.1021/om1003072](https://doi.org/10.1021/om1003072).

[62] J. Schulz, S. Levigne, A. Roucoux, H. Patin, *Adv. Synth. Catal.*, **2002**, *344*, 266–269. DOI: [10.1002/1615-4169(200206)344:3<266::AID-ADSC266>3.0.CO;2-O](https://doi.org/10.1002/1615-4169(200206)344:3<266::AID-ADSC266>3.0.CO;2-O).

[63] N. Yan, Y. Yuan, P. J. Dyson, *Chem. Comm.*, **2011**, *47*, 2529–2531. DOI: [10.1039/c0cc04641h](https://doi.org/10.1039/c0cc04641h).
[64] J. Schulz, A. Roucoux, H. Patin, *Chem. Eur. J.*, **2000**, *6*, 618–624. DOI: **10.1002/(sici)1521-3765(20000218)6:4<618::aid-chem618>3.0.co;2-a**.

[65] C. Vollmer, E. Redel, K. Abu-Shandi, R. Thomann, H. Manyar, C. Hardacre, C. Janiak, *Chem. Eur. J.*, **2010**, *16*, 3849–3858. DOI: **10.1002/chem.200903214**.

[66] E. Baralt, S. J. Smith, J. Hurwitz, I. T. Horváth, R. H. Fish, *J. Am. Chem. Soc.*, **1992**, *114*, 5187–5196. DOI: **10.1021/ja00039a033**.

[67] H. Imai, T. Nishiguchi, K. Fukuzumi, *J. Org. Chem.*, **1977**, *42*, 431–434. DOI: **10.1021/jo00433a024**.

[68] E. Baráth, *Catalysts*, **2018**, *8*, 671. DOI: **10.3390/catal8120671**.

[69] M. Studer, C. Wedemeyer-Exl, F. Spindler, H. U. Blaser, *Monatsh. Chem.*, **2000**, *131*, 1335–1343. DOI: **10.1016/S1381-1169(98)00200-3**.

[70] C. J. Abou-Fayssal, C. Fliedel, R. Poli, A. Riisager, K. Philippot, E. Manoury, *Mater. Today Chem.*, **2023**, *4*, 101752. DOI: **10.1016/j.mtchem.2023.101752**.

[71] M. A. Gelesky, S. S. X. Chiaro, F. A. Pavan, J. H. Z. dos Santos, J. Dupont, *Dalton Trans.*, **2007**, 5546–5548. DOI: **10.1039/B708111A**.

[72] L. M. Rossi, L. L. R. Vono, M. A. S. Garcia, T. L. T. Faria, J. A. Lopez-Sanchez, *Top. Catal.*, **2013**, *56*, 1228–1238. DOI: **10.1007/s11244-013-0089-z**.

[73] F. Martinez-Espinar, P. Blondeau, P. Nolis, B. Chaudret, C. Claver, S. Castillón, C. Godard, *J. Catal.*, **2017**, *354*, 113–127. DOI: **10.1016/j.jcat.2017.08.010**.

[74] M. Ibrahim, M. A. S. Garcia, L. L. R. Vono, M. Guerrero, P. Lecante, L. M. Rossi, K. Philippot, *Dalton Trans.*, **2016**, *45*, 17782–17791. DOI: **10.1039/c6dt03104h**.

[75] G. Vitulli, C. Evangelisti, P. Pertici, A. M. Caporusso, N. Panziera, P. Salvadori, M. G. Faga, C. Manfredotti, G. Martra, S. Coluccia, A. Balerna, S. Colonna, S. Mobilio, *J. Organomet. Chem.*, **2003**, *681*, 37–50. DOI: **10.1016/S0022-328X(03)00529-1**.

[76] H. Bin Pan, C. M. Wai, *J. Phys. Chem. C*, **2010**, *114*, 11364–11369. DOI: **10.1021/jp101368p**.

[77] T. T. Nguyen, P. Serp, *ChemCatChem*, **2013**, *5*, 3595–3603. DOI: **10.1002/cctc.201300527**.

[78] M. M. M. Jansen, J. Gracia, B. E. Nieuwenhuys, J. W. Niemantsverdriet, *Phys. Chem. Chem. Phys.*, **2009**, *11*, 10009–10016. DOI: **10.1039/b910497f**.

[79] S. Murphy, C. Strebel, S. B. Vendelbo, C. Conradsen, Y. Tison, K. Nielsen, L. Bech, R. M. Nielsen, M. Johansson, I. Chorkendorff, J. H. Nielsen, *Phys. Chem. Chem. Phys.*, **2011**, *13*, 10333–10341. DOI: **10.1039/c1cp20371a**.

[80] G. B. Deacon, J. H. S. Green, *Spectrochim. Acta A*, **1968**, *24*, 845–852. DOI: **10.1016/0584-8539(68)80183-7**.

[81] K. Senevirathne, A. W. Burns, M. E. Bussell, S. L. Brock, *Adv. Funct. Mater.*, **2007**, *17*, 3933–3939. DOI: **10.1002/adfm.200700758**.

[82] S. Carenco, C. Boissière, L. Nicole, C. Sanchez, P. Le Floch, N. Mézailles, *Chem. Mater.*, **2010**, *22*, 1340–1349. DOI: **10.1021/cm902007g**.

[83] C. Betti, J. Badano, C. Lederhos, M. Maccarrone, N. Carrara, F. Coloma-Pascual, M. Quiroga, C. Vera, *React. Kinet. Mech. Catal.*, **2016**, *117*, 283–306. DOI: **10.1007/s11144-015-0910-8**.

[84] J. A. Widegren, R. G. Finke, *J. Mol. Catal. A*, **2003**, *198*, 317–341. DOI: **10.1016/S1381-1169(02)00728-8**.

[85] C. Guminski, *J. Phase Equil.*, **2002**, *23*, 537–540. DOI: **10.1361/105497102770331280**.
[64] J. Schulz, A. Roucoux, H. Patin, *Chem. Eur. J.*, **2000**, *6*, 618–624. DOI: **10.1002/(sici)1521-3765(20000218)6:4<618::aid-chem618>3.0.co;2-a**.

[65] C. Vollmer, E. Redel, K. Abu-Shandi, R. Thomann, H. Manyar, C. Hardacre, C. Janiak, *Chem. Eur. J.*, **2010**, *16*, 3849–3858. DOI: **10.1002/chem.200903214**.

[66] E. Baralt, S. J. Smith, J. Hurwitz, I. T. Horváth, R. H. Fish, *J. Am. Chem. Soc.*, **1992**, *114*, 5187–5196. DOI: **10.1021/ja00039a033**.

[67] H. Imai, T. Nishiguchi, K. Fukuzumi, *J. Org. Chem.*, **1977**, *42*, 431–434. DOI: **10.1021/jo00433a024**.

[68] E. Baráth, *Catalysts*, **2018**, *8*, 671. DOI: **10.3390/catal8120671**.

[69] M. Studer, C. Wedemeyer-Exl, F. Spindler, H. U. Blaser, *Monatsh. Chem.*, **2000**, *131*, 1335–1343. DOI: **10.1016/S1381-1169(98)00200-3**.

[70] C. J. Abou-Fayssal, C. Fliedel, R. Poli, A. Riisager, K. Philippot, E. Manoury, *Mater. Today Chem.*, **2023**, *4*, 101752. DOI: **10.1016/j.mtchem.2023.101752**.

[71] M. A. Gelesky, S. S. X. Chiaro, F. A. Pavan, J. H. Z. dos Santos, J. Dupont, *Dalton Trans.*, **2007**, 5546–5548. DOI: **10.1039/B708111A**.

[72] L. M. Rossi, L. L. R. Vono, M. A. S. Garcia, T. L. T. Faria, J. A. Lopez-Sanchez, *Top. Catal.*, **2013**, *56*, 1228–1238. DOI: **10.1007/s11244-013-0089-z**.

[73] F. Martinez-Espinar, P. Blondeau, P. Nolis, B. Chaudret, C. Claver, S. Castillón, C. Godard, *J. Catal.*, **2017**, *354*, 113–127. DOI: **10.1016/j.jcat.2017.08.010**.

[74] M. Ibrahim, M. A. S. Garcia, L. L. R. Vono, M. Guerrero, P. Lecante, L. M. Rossi, K. Philippot, *Dalton Trans.*, **2016**, *45*, 17782–17791. DOI: **10.1039/c6dt03104h**.

[75] G. Vitulli, C. Evangelisti, P. Pertici, A. M. Caporusso, N. Panziera, P. Salvadori, M. G. Faga, C. Manfredotti, G. Martra, S. Coluccia, A. Balerna, S. Colonna, S. Mobilio, *J. Organomet. Chem.*, **2003**, *681*, 37–50. DOI: **10.1016/S0022-328X(03)00529-1**.

[76] H. Bin Pan, C. M. Wai, *J. Phys. Chem. C*, **2010**, *114*, 11364–11369. DOI: **10.1021/jp101368p**.

[77] T. T. Nguyen, P. Serp, *ChemCatChem*, **2013**, *5*, 3595–3603. DOI: **10.1002/cctc.201300527**.

[78] M. M. M. Jansen, J. Gracia, B. E. Nieuwenhuys, J. W. Niemantsverdriet, *Phys. Chem. Chem. Phys.*, **2009**, *11*, 10009–10016. DOI: **10.1039/b910497f**.

[79] S. Murphy, C. Strebel, S. B. Vendelbo, C. Conradsen, Y. Tison, K. Nielsen, L. Bech, R. M. Nielsen, M. Johansson, I. Chorkendorff, J. H. Nielsen, *Phys. Chem. Chem. Phys.*, **2011**, *13*, 10333–10341. DOI: **10.1039/c1cp20371a**.

[80] G. B. Deacon, J. H. S. Green, *Spectrochim. Acta A*, **1968**, *24*, 845–852. DOI: **10.1016/0584-8539(68)80183-7**.

[81] K. Senevirathne, A. W. Burns, M. E. Bussell, S. L. Brock, *Adv. Funct. Mater.*, **2007**, *17*, 3933–3939. DOI: **10.1002/adfm.200700758**.

[82] S. Carenco, C. Boissière, L. Nicole, C. Sanchez, P. Le Floch, N. Mézailles, *Chem. Mater.*, **2010**, *22*, 1340–1349. DOI: **10.1021/cm902007g**.

[83] C. Betti, J. Badano, C. Lederhos, M. Maccarrone, N. Carrara, F. Coloma-Pascual, M. Quiroga, C. Vera, *React. Kinet. Mech. Catal.*, **2016**, *117*, 283–306. DOI: **10.1007/s11144-015-0910-8**.

[84] J. A. Widegren, R. G. Finke, *J. Mol. Catal. A*, **2003**, *198*, 317–341. DOI: **10.1016/S1381-1169(02)00728-8**.

[85] C. Guminski, *J. Phase Equil.*, **2002**, *23*, 537–540. DOI: **10.1361/105497102770331280**.
Joel CEJAS SÁNCHEZ

ESR10

**Thesis co-directors**

Prof. Karol Grela Uniwersytet Warszawski, Warsaw, Poland

Prof. Rosa Maria Sebastián Universitat Autònoma de Barcelona, Bellaterra, Spain

**Thesis defense**

Department of Chemistry, University of Warsaw, 16 February 2024
Joel CEJAS SÁNCHEZ

ESR10

**Thesis co-directors**

Prof. Karol Grela Uniwersytet Warszawski, Warsaw, Poland

Prof. Rosa Maria Sebastián Universitat Autònoma de Barcelona, Bellaterra, Spain

**Thesis defense**

Department of Chemistry, University of Warsaw, 16 February 2024
<figure><img src="image_229.png" /></figure>
<figure><img src="image_227.png" /></figure>
# Immobilization of Ruthenium Complexes on Supports. Applications in Catalysis

## Introduction

Immobilized catalysts play a key role in advancing modern and sustainable chemistry, by means of anchoring a catalyst onto supports to facilitate its recovery, recycling, and reuse [1]. This approach offers several advantages, including the potential for enhanced catalyst activity, ease of handling and recovery through straightforward procedures, and the ability to reduce metal contamination in the final products [2,3]. With the ultimate goal of obtaining novel supported ruthenium complexes for their application in catalytic reactions, this Thesis has focused on the development of polyphosphorhydrazone-based (PPH) Janus dendrimers for grafting Ru-complexes and their applications in catalysis; and the preparation of novel Ru-NHC complexes and their immobilization on dendrimers and MOFs for olefin metathesis catalysis.

Bearing the previous approach in mind, one of the key objectives of this dissertation was the development of phosphorus Janus dendrimers as innovative catalyst supports. These novel dendrimers were expected to bridge the gap between homogeneous and heterogeneous catalysis, leading to the synthesis of a system that would behave as a homogeneous catalyst but possesses the recoverability and reusability possibilities of a heterogeneous approach [4]. Specifically, this project also aimed to immobilize ruthenium pre-catalysts onto the structure of phosphorus Janus dendrimers for applications in environmentally friendly solvents such as water. To achieve this, novel ruthenium complexes with unsymmetrical NHC ligands are synthesized, incorporating functionalities that enable their coupling to phosphorus Janus dendrimers. Simultaneously, these Janus dendrimers are designed to incorporate polyoxyethylenated chains to enhance water solubility, along with specific functional groups enabling the immobilization of the desired ligand/metal pre-catalyst. The synthesis of phosphorus Janus dendrimers is pursued through dendron synthesis and coupling procedures, to establish a comprehensive protocol for grafting dendrimeric halves. The prepared dendrimers will be assessed for their ability to immobilize ruthenium pre-catalysts, and the dendritic effect on the catalytic entity's activity and selectivity will be analyzed.

Furthermore, the versatility of both Ru-NHC complexes and phosphorus Janus dendrimers is set to be explored in parallel projects. In this context, the dendrimer capacity to graft alternative ruthenium complexes and their performance in environmentally friendly solvent catalysis will be evaluated. This evaluation also aimed to compare the catalytic performance –in terms of activity, efficiency, and recyclability of these systems– with single, non-immobilized versions of the same catalysts. Concurrently, the immobilization of Ru-NHC metathesis catalysts on heterogeneous supports (MOFs) was planned to assess their suitability for developing alternative approaches to catalytic system development.

## Synthesis of modified PPH Janus dendrimers for induced solubility in water

The initial part of this Thesis was dedicated to the synthesis of innovative PPH Janus dendrimers [5], designed to incorporate water-soluble PEG moieties on one side of the structure while featuring functional –P(S)Cl₂ groups for ligand/metal pre-catalyst integration on the opposite side (Figure 1). In this context, the synthesis of dendrimeric structures imparting dual properties to the final structure
# Immobilization of Ruthenium Complexes on Supports. Applications in Catalysis

## Introduction

Immobilized catalysts play a key role in advancing modern and sustainable chemistry, by means of anchoring a catalyst onto supports to facilitate its recovery, recycling, and reuse [1]. This approach offers several advantages, including the potential for enhanced catalyst activity, ease of handling and recovery through straightforward procedures, and the ability to reduce metal contamination in the final products [2,3]. With the ultimate goal of obtaining novel supported ruthenium complexes for their application in catalytic reactions, this Thesis has focused on the development of polyphosphorhydrazone-based (PPH) Janus dendrimers for grafting Ru-complexes and their applications in catalysis; and the preparation of novel Ru-NHC complexes and their immobilization on dendrimers and MOFs for olefin metathesis catalysis.

Bearing the previous approach in mind, one of the key objectives of this dissertation was the development of phosphorus Janus dendrimers as innovative catalyst supports. These novel dendrimers were expected to bridge the gap between homogeneous and heterogeneous catalysis, leading to the synthesis of a system that would behave as a homogeneous catalyst but possesses the recoverability and reusability possibilities of a heterogeneous approach [4]. Specifically, this project also aimed to immobilize ruthenium pre-catalysts onto the structure of phosphorus Janus dendrimers for applications in environmentally friendly solvents such as water. To achieve this, novel ruthenium complexes with unsymmetrical NHC ligands are synthesized, incorporating functionalities that enable their coupling to phosphorus Janus dendrimers. Simultaneously, these Janus dendrimers are designed to incorporate polyoxyethylenated chains to enhance water solubility, along with specific functional groups enabling the immobilization of the desired ligand/metal pre-catalyst. The synthesis of phosphorus Janus dendrimers is pursued through dendron synthesis and coupling procedures, to establish a comprehensive protocol for grafting dendrimeric halves. The prepared dendrimers will be assessed for their ability to immobilize ruthenium pre-catalysts, and the dendritic effect on the catalytic entity's activity and selectivity will be analyzed.

Furthermore, the versatility of both Ru-NHC complexes and phosphorus Janus dendrimers is set to be explored in parallel projects. In this context, the dendrimer capacity to graft alternative ruthenium complexes and their performance in environmentally friendly solvent catalysis will be evaluated. This evaluation also aimed to compare the catalytic performance –in terms of activity, efficiency, and recyclability of these systems– with single, non-immobilized versions of the same catalysts. Concurrently, the immobilization of Ru-NHC metathesis catalysts on heterogeneous supports (MOFs) was planned to assess their suitability for developing alternative approaches to catalytic system development.

## Synthesis of modified PPH Janus dendrimers for induced solubility in water

The initial part of this Thesis was dedicated to the synthesis of innovative PPH Janus dendrimers [5], designed to incorporate water-soluble PEG moieties on one side of the structure while featuring functional –P(S)Cl₂ groups for ligand/metal pre-catalyst integration on the opposite side (Figure 1). In this context, the synthesis of dendrimeric structures imparting dual properties to the final structure
was envisioned to achieve the first-ever reported functional metal@dendrimer system for catalysis with documented applications. To achieve this, phosphorus dendrimers were crafted employing two distinct dendron structures. Each dendron bore either an acetylene or azide group at the core level to enable subsequent coupling. These dendrimers were grown up to the second generation, and the desired Janus dendrimer was then created through click chemistry, which facilitated the fusion of the two targeted dendrons by forming a 1,2,3-triazole.

<figure><img src="image_230.png" /><figcaption>**Figure 28.** Schematic representation of the goal Janus dendrimer, bearing PEG chains to provide water solubility on one side (right, blue), and a grafting point for the incorporation of ligands/metal complexes (left, orange) for its use in supported aqueous catalytic reactions.</figcaption></figure>

The synthesis of dendrons commenced with the preparation of the desired azide and acetylene derivatives, which were developed as phenol-based structures due to the well-documented reactivity of phenols with PPH dendrimers. In particular, the synthesis of 4-(2-azidoethyl)phenol (2) and 4-(prop-2-yn-1-yloxy)phenol (3) was performed following previously reported methodologies [6–8]. Having successfully obtained the two desired azido and acetylenic phenol derivatives, the next step in synthesizing the dendrons was to introduce 2 and 3 to the hexafunctionalized dendrimer core ($N_3P_3Cl_6$) to create the monosubstituted cores (Scheme 1, top). Specifically, the methodology explored for dendron synthesis aimed at preparing $AB_5$-type dendrons, wherein one functionality at the core level would differ from the remaining five [9]. In the context of the dendritic systems of interest, this meant that the substitution of the core was carried out in such a way that five functionalities were employed for dendrimer growth, while the sixth functionality was the azide or acetylene derivative (compounds 2 and 3). This method involved the introduction of the azide/acetylene derivative initially, followed by the subsequent penta-substitution with 4-hydroxybenzaldehyde in a second step.

In this regard, the synthesis of the azido and acetylenic dendrons was pursued as shown in Scheme 1. First, the monosubstituted core derivatives 4 and 5 were synthesized by a selective monosubstitution reaction of one P-Cl bond from the $N_3P_3Cl_6$ core, and these structures were used as the starting building block for the creation of the dendron structures following the previously established methodologies by Caminade and Majoral [9,10]. The methodology consisted of the reaction of the remaining five P-Cl bonds with 4-hydroxybenzaldehyde to form the $G_0'$ dendrons, followed by the reaction of the terminal aldehyde groups from the $G_0'$ dendrons with N-methyldichlorothiophosphorhydrazide (9), which would lead to the obtention of highly functionalizable $-P(S)Cl_2$ groups. This way, first-generation dendrons were prepared for both azide (10-[G1]) and acetylene (11-[G1]) derivatives, which after stepwise synthesis also were crafted to the second generation (for the azide derivative 13-[G2], Scheme 1, bottom), leading to the obtention of a compound with twenty P-Cl surface functionalities.
was envisioned to achieve the first-ever reported functional metal@dendrimer system for catalysis with documented applications. To achieve this, phosphorus dendrimers were crafted employing two distinct dendron structures. Each dendron bore either an acetylene or azide group at the core level to enable subsequent coupling. These dendrimers were grown up to the second generation, and the desired Janus dendrimer was then created through click chemistry, which facilitated the fusion of the two targeted dendrons by forming a 1,2,3-triazole.

<figure><img src="image_228.png" /><figcaption>**Figure 28.** Schematic representation of the goal Janus dendrimer, bearing PEG chains to provide water solubility on one side (right, blue), and a grafting point for the incorporation of ligands/metal complexes (left, orange) for its use in supported aqueous catalytic reactions.</figcaption></figure>

The synthesis of dendrons commenced with the preparation of the desired azide and acetylene derivatives, which were developed as phenol-based structures due to the well-documented reactivity of phenols with PPH dendrimers. In particular, the synthesis of 4-(2-azidoethyl)phenol (2) and 4-(prop-2-yn-1-yloxy)phenol (3) was performed following previously reported methodologies [6–8]. Having successfully obtained the two desired azido and acetylenic phenol derivatives, the next step in synthesizing the dendrons was to introduce 2 and 3 to the hexafunctionalized dendrimer core ($N_3P_3Cl_6$) to create the monosubstituted cores (Scheme 1, top). Specifically, the methodology explored for dendron synthesis aimed at preparing $AB_5$-type dendrons, wherein one functionality at the core level would differ from the remaining five [9]. In the context of the dendritic systems of interest, this meant that the substitution of the core was carried out in such a way that five functionalities were employed for dendrimer growth, while the sixth functionality was the azide or acetylene derivative (compounds 2 and 3). This method involved the introduction of the azide/acetylene derivative initially, followed by the subsequent penta-substitution with 4-hydroxybenzaldehyde in a second step.

In this regard, the synthesis of the azido and acetylenic dendrons was pursued as shown in Scheme 1. First, the monosubstituted core derivatives 4 and 5 were synthesized by a selective monosubstitution reaction of one P-Cl bond from the $N_3P_3Cl_6$ core, and these structures were used as the starting building block for the creation of the dendron structures following the previously established methodologies by Caminade and Majoral [9,10]. The methodology consisted of the reaction of the remaining five P-Cl bonds with 4-hydroxybenzaldehyde to form the $G_0'$ dendrons, followed by the reaction of the terminal aldehyde groups from the $G_0'$ dendrons with N-methyldichlorothiophosphorhydrazide (9), which would lead to the obtention of highly functionalizable $-P(S)Cl_2$ groups. This way, first-generation dendrons were prepared for both azide (10-[G1]) and acetylene (11-[G1]) derivatives, which after stepwise synthesis also were crafted to the second generation (for the azide derivative 13-[G2], Scheme 1, bottom), leading to the obtention of a compound with twenty P-Cl surface functionalities.
<figure><img src="image_231.png" /><figcaption>**Scheme 56.** Overview of the synthetic approach performed for the synthesis of PPH AB₅-type dendrons bearing either azide or acetylene groups at the level of the core, up to the second-generation structures.</figcaption></figure>

Upon synthesis of dendrons up to the second generation, the focus shifted towards developing a dendron that could induce solubility in water, by the introduction of PEG chains. To achieve this objective, the synthesis of **14** (4-(2-(2-(2-methoxyethoxy)ethoxy)-ethoxy)phenol) was undertaken for the later surface modification of **10-[G₁]** azide dendron. PEG-modified phenol **14** was synthesized in two steps from hydroquinone and 2-(2-(2-methoxyethoxy)ethoxy)ethan-1-ol as previously reported [11], and later tested for the incorporation onto the dendron structure (Scheme 2). Of interest, phenol
<figure><img src="image_229.png" /><figcaption>**Scheme 56.** Overview of the synthetic approach performed for the synthesis of PPH AB~5~-type dendrons bearing either azide or acetylene groups at the level of the core, up to the second-generation structures.</figcaption></figure>

Upon synthesis of dendrons up to the second generation, the focus shifted towards developing a dendron that could induce solubility in water, by the introduction of PEG chains. To achieve this objective, the synthesis of **14** (4-(2-(2-(2-methoxyethoxy)ethoxy)-ethoxy)phenol) was undertaken for the later surface modification of **10-[G₁]** azide dendron. PEG-modified phenol **14** was synthesized in two steps from hydroquinone and 2-(2-(2-methoxyethoxy)ethoxy)ethan-1-ol as previously reported [11], and later tested for the incorporation onto the dendron structure (Scheme 2). Of interest, phenol
14 (in slight excess) was dissolved in THF and stirred at 0 °C in the presence of $Cs_2CO_3$ for 2 h before the addition of 10-[G₁], leading to the formation of the desired 15-[G₁]-PEG in moderate yields.

Upon synthesis of the desired functionalized dendrons, the preparation of Janus dendrimers was undertaken by the preparation of a hybrid 13-[G₀』][G₁]-PEG dendrimer (Scheme 2) was performed by reacting the PEG-modified azide dendron 15-[G₁]-PEG and the acetylene dendron 8-[G₀』 in stoichiometric amounts by the formation of a 1,2,3-triazole through a “click” copper-catalyzed azide-alkyne cycloaddition at 45 °C in presence of N,N-diisopropylethylamine (DIPEA) and Cul as catalyst. Lastly, the final stage in obtaining the desired first-generation Janus dendrimer involved extending the aldehyde functionalities of 16-[G₀』][G₁]-PEG to the full first generation 17-[G₁][G₁]-PEG (Scheme 2). It entailed the reaction of 16-[G₀』][G₁]-PEG with N-methyldichlorothiophosphorhydrazide 9 in the presence of anhydrous $Na_2SO_4$, as previously described for the growing of dendrons [12]. This led to the obtention of the targeted Janus dendrimer, bearing ten PEG chains on one side of the structure and ten P-Cl bonds on the other, ready to be coupled with the corresponding ligand or pre-catalyst of interest.

<figure><img src="image_232.png" /><figcaption>**Scheme 57.** Overview of the synthetic approach for the synthesis of a first-generation PPH Janus dendrimer 17-[G₁][G₁]-PEG by the combination of two dendrons though “click” chemistry.</figcaption></figure>

## Synthesis of a Ru(p-cymene)@Janus dendrimer catalytic system

To evaluate the applications of supported ruthenium complexes in catalysis, the next part of the Thesis was dedicated to preparing a metal@dendrimer system for catalytic applications in water-based systems. Based on the previous literature knowledge, the idea of preparing a novel Ru@dendrimer system was conceived. Therefore, the objective was to develop a novel catalytic system through the immobilization of metal pre-catalysts on the surface of the Janus dendrimer 17-[G₁][G₁]-PEG.
14 (in slight excess) was dissolved in THF and stirred at 0 °C in the presence of $Cs_2CO_3$ for 2 h before the addition of 10-[G₁], leading to the formation of the desired 15-[G₁]-PEG in moderate yields.

Upon synthesis of the desired functionalized dendrons, the preparation of Janus dendrimers was undertaken by the preparation of a hybrid 13-[G₀』][G₁]-PEG dendrimer (Scheme 2) was performed by reacting the PEG-modified azide dendron 15-[G₁]-PEG and the acetylene dendron 8-[G₀』 in stoichiometric amounts by the formation of a 1,2,3-triazole through a “click” copper-catalyzed azide-alkyne cycloaddition at 45 °C in presence of N,N-diisopropylethylamine (DIPEA) and Cul as catalyst. Lastly, the final stage in obtaining the desired first-generation Janus dendrimer involved extending the aldehyde functionalities of 16-[G₀』][G₁]-PEG to the full first generation 17-[G₁][G₁]-PEG (Scheme 2). It entailed the reaction of 16-[G₀』][G₁]-PEG with N-methyldichlorothiophosphorhydrazide 9 in the presence of anhydrous $Na_2SO_4$, as previously described for the growing of dendrons [12]. This led to the obtention of the targeted Janus dendrimer, bearing ten PEG chains on one side of the structure and ten P-Cl bonds on the other, ready to be coupled with the corresponding ligand or pre-catalyst of interest.

<figure><img src="image_230.png" /><figcaption>**Scheme 57.** Overview of the synthetic approach for the synthesis of a first-generation PPH Janus dendrimer 17-[G₁][G₁]-PEG by the combination of two dendrons though “click” chemistry.</figcaption></figure>

## Synthesis of a Ru(p-cymene)@Janus dendrimer catalytic system

To evaluate the applications of supported ruthenium complexes in catalysis, the next part of the Thesis was dedicated to preparing a metal@dendrimer system for catalytic applications in water-based systems. Based on the previous literature knowledge, the idea of preparing a novel Ru@dendrimer system was conceived. Therefore, the objective was to develop a novel catalytic system through the immobilization of metal pre-catalysts on the surface of the Janus dendrimer 17-[G₁][G₁]-PEG.
Specifically, it was aimed to immobilize [Ru($p$-cymene)Cl$_2$]$_2$ complexes on the dendrimer surface, based on the ease of availability of such compound.

The synthesis of the Ru@Janus dendrimer system commenced with the preparation of a phosphine ligand (4-(diphenylphosphoryl)phenol 21), which would be introduced onto the dendrimer structure before complexation of the pre-catalyst. This compound was chosen due to the presence of both a phenol group –which serves as a grafting point for the reaction with 17-[G$_1$][G$_1$]-PEG– and the phosphine itself, which would be used for the complexation of the ruthenium catalyst. The desired phenol phosphine 21 was synthesized in three steps from 4-bromophenol (Scheme 3) [13]: first, 4-bromophenol was derivatized to introduce a silyl protecting group by reaction with TBDMSCl; later, the conversion into phosphine by a two-step lithiation and phosphination with chlorodiphenyl phosphine; and lastly, the phenolic OH group was regenerated by deprotection with tetrabutylammonium fluoride (TBAF) to reach the desired 21 in 84% yield over three steps.

<figure><img src="image_233.png" /><figcaption>**Scheme 58.** Synthesis of 4-(diphenylphosphoryl)phenol (21) from 4-bromophenol</figcaption></figure>

After the synthesis of 21, the next step involved introducing it to the first-generation Janus dendrimer 17-[G$_1$][G$_1$]-PEG (Scheme 4). To prepare the desired phosphine-terminated dendrimer, standard reaction conditions for the introduction of phenol derivatives to –P(S)Cl$_2$-terminated dendrimers were employed, allowing the obtention of the desired phosphine-terminated 22-[G$_1$][G$_1$]-PEG in a moderate 55% yield after work-up. Lastly, the targeted Ru@dendrimer system was obtained by anchoring to the phosphine-terminated dendron 22-[G$_1$][G$_1$]-PEG a commercially available ruthenium complex. To accomplish this, [Ru($p$-cymene)Cl$_2$]$_2$ was grafted to the dendrimer through the complexation ability of the terminal phosphines. As illustrated in Scheme 4, five equivalents of the ruthenium complex were reacted with one equivalent of dendrimer 22-[G$_1$][G$_1$]-PEG –bearing ten phosphine groups– in THF at room temperature, following a similar procedure as previously reported in the literature [14]. The reaction proceeded smoothly, yielding the expected 23-Ru@[G$_1$][G$_1$]-PEG dendrimer as an orange solid in good yield, which was easily purified by precipitation and further washings. The newly formed Ru@dendrimer species was fully characterized, with special mention to the $ ^{31}P^{1}H} $ NMR, revealing a significant deshielding effect of the terminal phosphine upon complexation. Furthermore, inductively coupled plasma (ICP) analysis was used for assessing the ruthenium content in the Janus dendrimer. The analysis demonstrated that the supported 23-Ru@[G$_1$][G$_1$]-PEG contained a Ru content of 9.1%, aligning with the calculated theoretical value.
Specifically, it was aimed to immobilize [Ru($p$-cymene)Cl$_2$]$_2$ complexes on the dendrimer surface, based on the ease of availability of such compound.

The synthesis of the Ru@Janus dendrimer system commenced with the preparation of a phosphine ligand (4-(diphenylphosphoryl)phenol 21), which would be introduced onto the dendrimer structure before complexation of the pre-catalyst. This compound was chosen due to the presence of both a phenol group –which serves as a grafting point for the reaction with 17-[G$_1$][G$_1$]-PEG– and the phosphine itself, which would be used for the complexation of the ruthenium catalyst. The desired phenol phosphine 21 was synthesized in three steps from 4-bromophenol (Scheme 3) [13]: first, 4-bromophenol was derivatized to introduce a silyl protecting group by reaction with TBDMSCl; later, the conversion into phosphine by a two-step lithiation and phosphination with chlorodiphenyl phosphine; and lastly, the phenolic OH group was regenerated by deprotection with tetrabutylammonium fluoride (TBAF) to reach the desired 21 in 84% yield over three steps.

<figure><img src="image_231.png" /><figcaption>**Scheme 58.** Synthesis of 4-(diphenylphosphoryl)phenol (21) from 4-bromophenol</figcaption></figure>

After the synthesis of 21, the next step involved introducing it to the first-generation Janus dendrimer 17-[G$_1$][G$_1$]-PEG (Scheme 4). To prepare the desired phosphine-terminated dendrimer, standard reaction conditions for the introduction of phenol derivatives to –P(S)Cl$_2$-terminated dendrimers were employed, allowing the obtention of the desired phosphine-terminated 22-[G$_1$][G$_1$]-PEG in a moderate 55% yield after work-up. Lastly, the targeted Ru@dendrimer system was obtained by anchoring to the phosphine-terminated dendron 22-[G$_1$][G$_1$]-PEG a commercially available ruthenium complex. To accomplish this, [Ru($p$-cymene)Cl$_2$]$_2$ was grafted to the dendrimer through the complexation ability of the terminal phosphines. As illustrated in Scheme 4, five equivalents of the ruthenium complex were reacted with one equivalent of dendrimer 22-[G$_1$][G$_1$]-PEG –bearing ten phosphine groups– in THF at room temperature, following a similar procedure as previously reported in the literature [14]. The reaction proceeded smoothly, yielding the expected 23-Ru@[G$_1$][G$_1$]-PEG dendrimer as an orange solid in good yield, which was easily purified by precipitation and further washings. The newly formed Ru@dendrimer species was fully characterized, with special mention to the $ ^{31}P^{1}H} $ NMR, revealing a significant deshielding effect of the terminal phosphine upon complexation. Furthermore, inductively coupled plasma (ICP) analysis was used for assessing the ruthenium content in the Janus dendrimer. The analysis demonstrated that the supported 23-Ru@[G$_1$][G$_1$]-PEG contained a Ru content of 9.1%, aligning with the calculated theoretical value.
<figure><img src="image_234.png" /><figcaption>**Scheme 59.** Synthesis of a Ru@Janus dendrimer 23-Ru[@[G₁][G₁]-PEG], bearing ten PEG moieties on one side of the structure and ten Ru(p-cymene) units in the other.</figcaption></figure>

Catalytic tests for the isomerization of allyl alcohols

Dendrimers can have various effects when applied in catalysis, including modifications of catalytic activity due to the high local concentration of catalysts within dendrimers, effects arising from catalyst anchoring, potential electronic modifications, and the facilitation of catalyst recyclability and reusability within dendrimeric systems [15,16]. To properly assess the performance of the novel immobilized ruthenium complex 23-Ru[@[G₁][G₁]-PEG], it was essential to synthesize analogous ruthenium complexes for comparison purposes. These novel structures were prepared following the synthetic approach depicted in Scheme 5, yielding to the obtention of monometallic (26) and bimetallic (29) structures, designed to mimic the surface of the Ru@dendrimer 23.
<figure><img src="image_232.png" /><figcaption>**Scheme 59.** Synthesis of a Ru@Janus dendrimer 23-Ru[@G₁][G₁]-PEG, bearing ten PEG moieties on one side of the structure and ten Ru(p-cymene) units in the other.</figcaption></figure>

## Catalytic tests for the isomerization of allyl alcohols

Dendrimers can have various effects when applied in catalysis, including modifications of catalytic activity due to the high local concentration of catalysts within dendrimers, effects arising from catalyst anchoring, potential electronic modifications, and the facilitation of catalyst recyclability and reusability within dendrimeric systems [15,16]. To properly assess the performance of the novel immobilized ruthenium complex 23-Ru[@G₁][G₁]-PEG, it was essential to synthesize analogous ruthenium complexes for comparison purposes. These novel structures were prepared following the synthetic approach depicted in Scheme 5, yielding to the obtention of monometallic (26) and bimetallic (29) structures, designed to mimic the surface of the Ru@dendrimer 23.
<figure><img src="image_235.png" /><figcaption>**Scheme 60.** Synthesis of Ru-complexes **26** and **29**, monometallic and bimetallic analogues of the Ru@dendrimer **23**, respectively.</figcaption></figure>

Having successfully synthesized a PPH Janus dendrimer system containing Ru(*p*-cymene) complexes within its structure (**23**), along with analogous monometallic and bimetallic species (**26**, **29**), the next step was to evaluate the catalytic activity of the three prepared complexes. Ru(*p*-cymene)-type complexes have been well-documented in the literature for their applications as catalysts in various processes, including the isomerization of allyl alcohols and the hydration of acetylenes, among others [17,18]. For the evaluation, the isomerization of allyl alcohols was selected as the target reaction to assess the performance of the prepared complexes. This reaction typically involves the conversion of allyl alcohols into ketones or aldehydes through a two-step process that combines oxidation and reduction, but that is carried out in a one-pot manner using organometallic complexes. The initial catalytic tests for the novel Ru-complexes were conducted to evaluate their performance for the isomerization of 1-octen-3-ol to 3-octanone, firstly in conventional organic solvent conditions. In these experiments, a THF solution containing the substrate **S1** (1.0 equiv.), 1,3,5-trimethoxybenzene (used as an internal standard), and $Cs_2CO_3$ (2 mol%) was prepared (Table 1). The reaction mixture was then heated to 75 °C, and 1 mol% of the ruthenium catalyst was added. It is worth noting that the same reaction conditions were applied for all three Ru-catalysts, and the conversion was assessed by gas chromatography (GC) comparing the crude mixtures with the original samples of substrates and products.

<table><caption>**Table 8.** Isomerization of 1-octen-3-ol to 3-octanone at 75 °C catalyzed by complexes **23**, **26** and **29** (1 mol% loading) with $Cs_2CO_3$ (2 mol%) as co-catalyst, under given solvent conditions.</caption><thead><tr><th>Entry</th><th>Catalyst</th><th>Solvent</th><th>Time to full conversion [h]<sup>a</sup></th></tr></thead><tbody><tr><td>1</td><td>26 - monometallic</td><td></td><td>3</td></tr><tr><td>2</td><td>29 - bimetallic</td><td>THF</td><td>1.5</td></tr><tr><td>3</td><td>23-Ru@[G<sub>1</sub>][G<sub>1</sub>]-PEG (10 [Ru])</td><td></td><td>1.5</td></tr><tr><td>4</td><td>26 - monometallic</td><td></td><td>-</td></tr><tr><td>5</td><td>29 - bimetallic</td><td>H<sub>2</sub>O/n-heptane</td><td>-</td></tr><tr><td>6</td><td>23-Ru@[G<sub>1</sub>][G<sub>1</sub>]-PEG (10 [Ru])</td><td></td><td>24</td></tr></tbody></table>

<footnote><sup>a</sup> Conversion was determined through GC using 1,3,5-trimethoxybenzene as internal standard.</footnote>
<figure><img src="image_233.png" /><figcaption>**Scheme 60.** Synthesis of Ru-complexes **26** and **29**, monometallic and bimetallic analogues of the Ru@dendrimer **23**, respectively.</figcaption></figure>

Having successfully synthesized a PPH Janus dendrimer system containing Ru(*p*-cymene) complexes within its structure (**23**), along with analogous monometallic and bimetallic species (**26**, **29**), the next step was to evaluate the catalytic activity of the three prepared complexes. Ru(*p*-cymene)-type complexes have been well-documented in the literature for their applications as catalysts in various processes, including the isomerization of allyl alcohols and the hydration of acetylenes, among others [17,18]. For the evaluation, the isomerization of allyl alcohols was selected as the target reaction to assess the performance of the prepared complexes. This reaction typically involves the conversion of allyl alcohols into ketones or aldehydes through a two-step process that combines oxidation and reduction, but that is carried out in a one-pot manner using organometallic complexes. The initial catalytic tests for the novel Ru-complexes were conducted to evaluate their performance for the isomerization of 1-octen-3-ol to 3-octanone, firstly in conventional organic solvent conditions. In these experiments, a THF solution containing the substrate **S1** (1.0 equiv.), 1,3,5-trimethoxybenzene (used as an internal standard), and $Cs_2CO_3$ (2 mol%) was prepared (Table 1). The reaction mixture was then heated to 75 °C, and 1 mol% of the ruthenium catalyst was added. It is worth noting that the same reaction conditions were applied for all three Ru-catalysts, and the conversion was assessed by gas chromatography (GC) comparing the crude mixtures with the original samples of substrates and products.

<table><caption>**Table 8.** Isomerization of 1-octen-3-ol to 3-octanone at 75 °C catalyzed by complexes **23**, **26** and **29** (1 mol% loading) with $Cs_2CO_3$ (2 mol%) as co-catalyst, under given solvent conditions.</caption><thead><tr><th>Entry</th><th>Catalyst</th><th>Solvent</th><th>Time to full conversion [h]<sup>a</sup></th></tr></thead><tbody><tr><td>1</td><td>26 - monometallic</td><td></td><td>3</td></tr><tr><td>2</td><td>29 - bimetallic</td><td>THF</td><td>1.5</td></tr><tr><td>3</td><td>23-Ru@[G<sub>1</sub>][G<sub>1</sub>]-PEG (10 [Ru])</td><td></td><td>1.5</td></tr><tr><td>4</td><td>26 - monometallic</td><td></td><td>-</td></tr><tr><td>5</td><td>29 - bimetallic</td><td>H<sub>2</sub>O/n-heptane</td><td>-</td></tr><tr><td>6</td><td>23-Ru@[G<sub>1</sub>][G<sub>1</sub>]-PEG (10 [Ru])</td><td></td><td>24</td></tr></tbody></table>

<footnote><sup>a</sup> Conversion was determined through GC using 1,3,5-trimethoxybenzene as internal standard.</footnote>
As anticipated, all three Ru-complexes achieved full conversion within the reported time frames in the literature (Table 1, entries 1-3) [17,18]. Monometallic complex **26** achieved full conversion after 3 hours of reaction. Remarkably, both the bimetallic complex **29** and the dendrimeric structure **23-Ru@[G₁][G₁]-PEG** yielded 3-octanone (P1) in short reaction times (1.5 h). These results were highly encouraging, as they indicated that the proximity of ruthenium centers could potentially lead to a cooperative effect, enhancing the efficiency of the reaction.

Following the promising results obtained in organic solvent conditions, the focus was shifted to utilizing water as the solvent for the catalytic process. Specifically, an *n*-heptane/water mixture (1:1) was chosen as the solvent system, considering it a valuable approach to reduce the usage of organic solvents by incorporation of a sustainable solvent such as water, and benefiting from the possibility of an easier recovery of the catalyst in biphasic media. Importantly, the presence of an *n*-heptane/water mixture resulted in the formation of a biphasic system where: (i) the substrate, product, and the internal standard resided in the organic *n*-heptane phase; and (ii) cesium carbonate and the Ru@dendrimer **23** remained in the water phase making easier its recovering and recycling. Catalytic tests were conducted following the previously established reaction conditions incorporating the use of a biphasic solvent system. Aliquots were sampled at specific intervals, and conversion was determined by GC (Table 1, entries 4-6). The catalytic results revealed that both the monometallic and bimetallic systems yielded no isomerization product after 24 hours of reaction. Intriguingly, when the **23-Ru@[G₁][G₁]-PEG** catalyst was employed, full conversion was achieved after 24 hours of reaction.

The obtained results were highly positive in terms of the activity of the Ru@dendrimer system. Notably, a positive dendritic effect was observed for the isomerization of 3-octen-1-ol in both organic solvent and biphasic mixtures. Particularly intriguing was the use of the biphasic system, where only **23-Ru@[G₁][G₁]-PEG** exhibited catalytic activity for the desired reaction, although activity was reduced, and long reaction times were required. Lastly, it was decided to investigate the recyclability of the dendrimeric system, to provide a greener approach to the use of a Ru@dendrimer catalyst. In this context, a catalytic test was conducted in the biphasic solvent conditions, and the reaction was allowed to proceed for 24 hours. After reaction time, the organic phase was separated from the aqueous phase and GC analyses confirmed the full conversion of **S1** to 3-octanone in the recovered phase. Subsequently, a mixture of **S1** and 1,3,5-trimethoxybenzene in fresh *n*-heptane was added to the water phase containing the Ru@dendrimer catalyst **23**. Repetition of this procedure resulted in the attainment of full conversion of 3-octanone for up to three consecutive runs (Figure 2). Moreover, the possibility of metal leaching was also investigated. Analysis of Ru content in the organic phase by ICP revealed no significant leaching, even after full conversion to 3-octenone. ICP results indicated the presence of less than 0.05% Ru contamination in the sample, confirming the excellent stability of the catalyst.

## Synthesis of unsymmetrical N-heterocyclic carbene (uNHC) ligands bearing a phenol handler

The significance and relevance of olefin metathesis catalysts are closely linked to the development of N-heterocyclic carbene (NHC) ligands. This connection primarily arises from the increased stability of Ru-NHC complexes compared to their phosphine counterparts [19]. Additionally, the ease of adjusting the electronic and steric properties of Ru-NHC complexes by modifying substituents within their structure further underscores their importance. Consequently, a wide range of NHC ligands have been developed in the literature, with most featuring symmetrical substituents in their structure. However, it is worth noting that, while unsymmetrical NHCs (uNHCs) generally exhibit
As anticipated, all three Ru-complexes achieved full conversion within the reported time frames in the literature (Table 1, entries 1-3) [17,18]. Monometallic complex **26** achieved full conversion after 3 hours of reaction. Remarkably, both the bimetallic complex **29** and the dendrimeric structure **23-Ru@[G₁][G₁]-PEG** yielded 3-octanone (P1) in short reaction times (1.5 h). These results were highly encouraging, as they indicated that the proximity of ruthenium centers could potentially lead to a cooperative effect, enhancing the efficiency of the reaction.

Following the promising results obtained in organic solvent conditions, the focus was shifted to utilizing water as the solvent for the catalytic process. Specifically, an *n*-heptane/water mixture (1:1) was chosen as the solvent system, considering it a valuable approach to reduce the usage of organic solvents by incorporation of a sustainable solvent such as water, and benefiting from the possibility of an easier recovery of the catalyst in biphasic media. Importantly, the presence of an *n*-heptane/water mixture resulted in the formation of a biphasic system where: (i) the substrate, product, and the internal standard resided in the organic *n*-heptane phase; and (ii) cesium carbonate and the Ru@dendrimer **23** remained in the water phase making easier its recovering and recycling. Catalytic tests were conducted following the previously established reaction conditions incorporating the use of a biphasic solvent system. Aliquots were sampled at specific intervals, and conversion was determined by GC (Table 1, entries 4-6). The catalytic results revealed that both the monometallic and bimetallic systems yielded no isomerization product after 24 hours of reaction. Intriguingly, when the **23-Ru@[G₁][G₁]-PEG** catalyst was employed, full conversion was achieved after 24 hours of reaction.

The obtained results were highly positive in terms of the activity of the Ru@dendrimer system. Notably, a positive dendritic effect was observed for the isomerization of 3-octen-1-ol in both organic solvent and biphasic mixtures. Particularly intriguing was the use of the biphasic system, where only **23-Ru@[G₁][G₁]-PEG** exhibited catalytic activity for the desired reaction, although activity was reduced, and long reaction times were required. Lastly, it was decided to investigate the recyclability of the dendrimeric system, to provide a greener approach to the use of a Ru@dendrimer catalyst. In this context, a catalytic test was conducted in the biphasic solvent conditions, and the reaction was allowed to proceed for 24 hours. After reaction time, the organic phase was separated from the aqueous phase and GC analyses confirmed the full conversion of **S1** to 3-octanone in the recovered phase. Subsequently, a mixture of **S1** and 1,3,5-trimethoxybenzene in fresh *n*-heptane was added to the water phase containing the Ru@dendrimer catalyst **23**. Repetition of this procedure resulted in the attainment of full conversion of 3-octanone for up to three consecutive runs (Figure 2). Moreover, the possibility of metal leaching was also investigated. Analysis of Ru content in the organic phase by ICP revealed no significant leaching, even after full conversion to 3-octenone. ICP results indicated the presence of less than 0.05% Ru contamination in the sample, confirming the excellent stability of the catalyst.

## Synthesis of unsymmetrical N-heterocyclic carbene (uNHC) ligands bearing a phenol handler

The significance and relevance of olefin metathesis catalysts are closely linked to the development of N-heterocyclic carbene (NHC) ligands. This connection primarily arises from the increased stability of Ru-NHC complexes compared to their phosphine counterparts [19]. Additionally, the ease of adjusting the electronic and steric properties of Ru-NHC complexes by modifying substituents within their structure further underscores their importance. Consequently, a wide range of NHC ligands have been developed in the literature, with most featuring symmetrical substituents in their structure. However, it is worth noting that, while unsymmetrical NHCs (uNHCs) generally exhibit
lower activity compared to their symmetrical counterparts, they hold promise as an attractive alternative for applications in non-conventional metathesis processes [20]. In this context, this thesis focuses on the development of novel uNHC ligands and their corresponding Hoveyda-II-type complexes.

<figure><img src="image_236.png" /><figcaption>**Figure 29.** Isomerization of 1-octen-3-ol to 3-octanone in n-heptane/water mixture at 75 °C catalyzed by complexes 23, 26 and 29 (1 mol%), showing a clear dendrimer effect; and recyclability experiments of dendrimer 23 up to three consecutive runs.</figcaption></figure>

Of particular interest is the creation of Ru-NHC complexes featuring functional groups suitable for attachment to various supports. This includes investigating their incorporation onto dendritic supports or metal-organic frameworks (MOFs). The selection of appropriate functional groups for the uNHCs is a critical aspect of this endeavor. To achieve the desired objective, this section aimed to outline the synthesis of unsymmetrical N-heterocyclic carbenes (uNHCs). These uNHCs were designed to incorporate a mesityl group on one side and a phenolic group on the other. Furthermore, the research will explore how the presence of uNHCs influences the reactivity of Ru-NHC complexes, as well as the impact of temperature and solvent on olefin metathesis catalysis to assess the suitability of these novel complexes for metathesis catalysis.

The synthesis of the Ru-NHC complexes was started by the synthesis of NHC precursors bearing the previously mentioned phenolic arm [21]. The synthesis of unsymmetrical imidazolium ligand precursors **34** and **40** was accomplished using two pathways: through the condensation of N-(2,4,6-trimethylphenyl)-1,2-diaminoethane with 4-hydroxybenzaldehyde in the presence of a catalytic amount of formic acid (for **35**, Scheme 6), further reduction of the imine **33** to the corresponding diamine **34**, followed by cyclization with triethyl orthoformate to give the NHC precursor **35**; or through simple alkylation of Mes (Mes = 2,4,6-trimethylphenyl)-bearing imidazole with **38** (iodomethyl)phenol (for **40**, Scheme 7).

The synthesis of unsymmetrical N-heterocyclic carbene (uNHC) Hoveyda–Grubbs-type II-generation complexes involved the exchange of the phosphine ligand of the Hoveyda–Grubbs-type-I-generation catalyst with a uNHC ligand (Scheme 8). The process included treating the corresponding ligand precursor (**35** or **40**) with LiHMDS to generate a carbene *in situ*, followed by reaction with the Hoveyda–Grubbs-type-I-generation catalyst. Quenching with 5 equivalents of 4 N HCl in dioxane "liberated" the OH-group and provided the desired complexes **Ru1** and **Ru2** in moderate yields. Interestingly, in the case of the **Ru2** complex, the exchange of Cl⁻ anions at the ruthenium coordination center to a labile iodide anion from the imidazolium ligand was observed. This phenomenon, known as "scrambling" [22], resulted in an undefined mixture of **Ru2** and **Ru3** complexes. To overcome this obstacle, it was decided to counter-exchange iodide anions to chlorides through treatment with silver
lower activity compared to their symmetrical counterparts, they hold promise as an attractive alternative for applications in non-conventional metathesis processes [20]. In this context, this thesis focuses on the development of novel uNHC ligands and their corresponding Hoveyda-II-type complexes.

<figure><img src="image_234.png" /><figcaption>**Figure 29.** Isomerization of 1-octen-3-ol to 3-octanone in n-heptane/water mixture at 75 °C catalyzed by complexes **23**, **26** and **29** (1 mol%), showing a clear dendrimer effect; and recyclability experiments of dendrimer **23** up to three consecutive runs.</figcaption></figure>

Of particular interest is the creation of Ru-NHC complexes featuring functional groups suitable for attachment to various supports. This includes investigating their incorporation onto dendritic supports or metal-organic frameworks (MOFs). The selection of appropriate functional groups for the uNHCs is a critical aspect of this endeavor. To achieve the desired objective, this section aimed to outline the synthesis of unsymmetrical N-heterocyclic carbenes (uNHCs). These uNHCs were designed to incorporate a mesityl group on one side and a phenolic group on the other. Furthermore, the research will explore how the presence of uNHCs influences the reactivity of Ru-NHC complexes, as well as the impact of temperature and solvent on olefin metathesis catalysis to assess the suitability of these novel complexes for metathesis catalysis.

The synthesis of the Ru-NHC complexes was started by the synthesis of NHC precursors bearing the previously mentioned phenolic arm [21]. The synthesis of unsymmetrical imidazolium ligand precursors **34** and **40** was accomplished using two pathways: through the condensation of N-(2,4,6-trimethylphenyl)-1,2-diaminoethane with 4-hydroxybenzaldehyde in the presence of a catalytic amount of formic acid (for **35**, Scheme 6), further reduction of the imine **33** to the corresponding diamine **34**, followed by cyclization with triethyl orthoformate to give the NHC precursor **35**; or through simple alkylation of Mes (Mes = 2,4,6-trimethylphenyl)-bearing imidazole with **38** (iodomethyl)phenol (for **40**, Scheme 7).

The synthesis of unsymmetrical N-heterocyclic carbene (uNHC) Hoveyda–Grubbs-type II-generation complexes involved the exchange of the phosphine ligand of the Hoveyda–Grubbs-type-I-generation catalyst with a uNHC ligand (Scheme 8). The process included treating the corresponding ligand precursor (**35** or **40**) with LiHMDS to generate a carbene *in situ*, followed by reaction with the Hoveyda–Grubbs-type-I-generation catalyst. Quenching with 5 equivalents of 4 N HCl in dioxane "liberated" the OH-group and provided the desired complexes **Ru1** and **Ru2** in moderate yields. Interestingly, in the case of the **Ru2** complex, the exchange of Cl⁻ anions at the ruthenium coordination center to a labile iodide anion from the imidazolium ligand was observed. This phenomenon, known as "scrambling" [22], resulted in an undefined mixture of **Ru2** and **Ru3** complexes. To overcome this obstacle, it was decided to counter-exchange iodide anions to chlorides through treatment with silver
chloride (1.1 equiv. per **Ru2** in DCM at room temperature). This simple transformation yielded the pure **Ru3** complex in practically quantitative yield. The synthesized imidazolium ligand precursors (35, 40) and catalysts (**Ru1**, **Ru3**) were fully characterized using a combination of NMR spectroscopy and HRMS (or elemental analysis), as well as IR spectroscopy. The chemical shifts of benzylidene protons of the obtained complexes ranged from 16.38 to 16.22 ppm, which is typical for this class of Hoveyda-type catalysts.

<figure><img src="image_237.png" /><figcaption>**Scheme 61.** Synthesis of the unsymmetrical NHC ligand precursor 35, bearing a phenolic arm in the structure.</figcaption></figure>

<figure><img src="image_238.png" /><figcaption>**Scheme 62.** Synthesis of 3-(4-hydroxybenzyl)-1-mesityl-1H-imidazol-3-ium iodide 40.</figcaption></figure>

<figure><img src="image_239.png" /><figcaption>**Scheme 63.** Synthesis of Ru-NHC complexes Ru1 and Ru3 bearing a phenolic arm in the structure.</figcaption></figure>
chloride (1.1 equiv. per **Ru2** in DCM at room temperature). This simple transformation yielded the pure **Ru3** complex in practically quantitative yield. The synthesized imidazolium ligand precursors (35, 40) and catalysts (**Ru1**, **Ru3**) were fully characterized using a combination of NMR spectroscopy and HRMS (or elemental analysis), as well as IR spectroscopy. The chemical shifts of benzylidene protons of the obtained complexes ranged from 16.38 to 16.22 ppm, which is typical for this class of Hoveyda-type catalysts.

<figure><img src="image_235.png" /><figcaption>**Scheme 61.** Synthesis of the unsymmetrical NHC ligand precursor 35, bearing a phenolic arm in the structure.</figcaption></figure>

<figure><img src="image_236.png" /><figcaption>**Scheme 62.** Synthesis of 3-(4-hydroxybenzyl)-1-mesityl-1H-imidazol-3-ium iodide 40.</figcaption></figure>

<figure><img src="image_237.png" /><figcaption>**Scheme 63.** Synthesis of Ru-NHC complexes Ru1 and Ru3 bearing a phenolic arm in the structure.</figcaption></figure>
Following the synthesis and characterization of the phenolic complexes **Ru1** and **Ru3**, the next step was to investigate the stability and activity of these complexes in solution. Concerning the stability studies, complexes **Ru1** and **Ru3** were dissolved in deuterated DCM ($C_{[Ru]}$ = 0.02 M) in an argon atmosphere at room temperature, followed by the addition of 1,3,5-trimethoxybenzene as an internal standard. The decomposition of the catalysts was quantified using ¹H NMR spectroscopy with respect to 1,3,5-trimethoxybenzene, measuring the decrease in the intensity of benzylidene signals in ¹H NMR spectra. Unfortunately, the analogous experiment performed in toluene failed due to precipitate formation. Both synthesized catalysts demonstrated high stability in deuterated DCM at room temperature, decomposing only 6% and 4% over 10 days (for **Ru1** and **Ru3**, respectively). Comparing these results to what was reported previously for structurally related uNHC catalysts shows a positive effect of the electron-donating OH-substituent in the *N*-benzyl “arm,” visibly stabilizing the ruthenium center against decomposition [23].

After the synthesis and stability assessments of **Ru1** and **Ru3**, the activity and reaction profiles of these "phenolic" complexes were examined. To do so, the ring-closing metathesis (RCM) reaction of diethyl diallyl malonate (DEDAM, **S2**) was evaluated as a model reaction. For this purpose, malonate **S2** was dissolved in DCM or toluene ($C_{[S2]}$ = 0.1 M) and treated with 1 mol% catalyst (**Ru1** or **Ru3**). The reaction was monitored through GC to determine the time-dependent conversion of **S2**. As expected, similar to the other members of this uNHC catalysts family, both of the studied catalysts were found to be less active under ambient conditions but sufficiently activated at slightly elevated temperatures (Table 2). In the case of **Ru1**, the RCM experiment at room temperature in DCM showed a maximum conversion of 49%, demonstrating a rather moderate activity of the catalyst under ambient conditions. Similarly, the RCM reaction of malonate **S2** was conducted using the unsaturated complex (**Ru3**). The outcome of this catalytic run was more positive—the conversion after 24 h reached 79%. When toluene was used as a solvent at 50 °C, both catalysts showed satisfactory results, driving the reaction to full conversion. In this case, too, higher activity of **Ru3** was observed compared to its saturated congener **Ru1**.

<table><caption>**Table 2.** Outcome of the RCM of DEDAM (**S2**) under various conditions (solvent, temperature, and addition of a Lewis acid) for **Ru1** and **Ru3**.</caption><thead><tr><th>Entry</th><th>[Ru]</th><th>Solvent</th><th>Additive</th><th>Temperature [°C]</th><th>Conversion [%]<sup>a</sup></th></tr></thead><tbody><tr><td>1</td><td rowspan="3">Ru1</td><td>DCM</td><td>—</td><td>RT</td><td>49</td></tr><tr><td>2</td><td>DCM</td><td>B(OEt)<sub>3</sub></td><td>RT</td><td>56</td></tr><tr><td>3</td><td>Toluene</td><td>—</td><td>50</td><td>&gt;99</td></tr><tr><td>4</td><td rowspan="2">Ru3</td><td>DCM</td><td>—</td><td>RT</td><td>79</td></tr><tr><td>5</td><td>Toluene</td><td>—</td><td>50</td><td>&gt;99</td></tr></tbody></table>

## Immobilization of Ru-NHC complexes on Metal-Organic Frameworks

Subsequently, we undertook the task of immobilizing the newly synthesized Ru-NHC complexes onto metal-organic frameworks (MOFs) as heterogeneous supports. For the immobilization of Ru-NHC on MOFs, the more active **Ru3** complex was selected as the candidate for immobilization. Considering the relatively large size of the Hoveyda–Grubbs-type complexes and the stability of a potential solid support, (Al)MIL-101-NH<sub>2</sub> was chosen, which met the aforementioned criteria [24].

<footnote><sup>a</sup> Conversion assessed by GC using dodecane as an internal standard</footnote>
Following the synthesis and characterization of the phenolic complexes **Ru1** and **Ru3**, the next step was to investigate the stability and activity of these complexes in solution. Concerning the stability studies, complexes **Ru1** and **Ru3** were dissolved in deuterated DCM ($C_{[Ru]}$ = 0.02 M) in an argon atmosphere at room temperature, followed by the addition of 1,3,5-trimethoxybenzene as an internal standard. The decomposition of the catalysts was quantified using ¹H NMR spectroscopy with respect to 1,3,5-trimethoxybenzene, measuring the decrease in the intensity of benzylidene signals in ¹H NMR spectra. Unfortunately, the analogous experiment performed in toluene failed due to precipitate formation. Both synthesized catalysts demonstrated high stability in deuterated DCM at room temperature, decomposing only 6% and 4% over 10 days (for **Ru1** and **Ru3**, respectively). Comparing these results to what was reported previously for structurally related uNHC catalysts shows a positive effect of the electron-donating OH-substituent in the *N*-benzyl “arm,” visibly stabilizing the ruthenium center against decomposition [23].

After the synthesis and stability assessments of **Ru1** and **Ru3**, the activity and reaction profiles of these "phenolic" complexes were examined. To do so, the ring-closing metathesis (RCM) reaction of diethyl diallyl malonate (DEDAM, **S2**) was evaluated as a model reaction. For this purpose, malonate **S2** was dissolved in DCM or toluene ($C_{[S2]}$ = 0.1 M) and treated with 1 mol% catalyst (**Ru1** or **Ru3**). The reaction was monitored through GC to determine the time-dependent conversion of **S2**. As expected, similar to the other members of this uNHC catalysts family, both of the studied catalysts were found to be less active under ambient conditions but sufficiently activated at slightly elevated temperatures (Table 2). In the case of **Ru1**, the RCM experiment at room temperature in DCM showed a maximum conversion of 49%, demonstrating a rather moderate activity of the catalyst under ambient conditions. Similarly, the RCM reaction of malonate **S2** was conducted using the unsaturated complex (**Ru3**). The outcome of this catalytic run was more positive—the conversion after 24 h reached 79%. When toluene was used as a solvent at 50 °C, both catalysts showed satisfactory results, driving the reaction to full conversion. In this case, too, higher activity of **Ru3** was observed compared to its saturated congener **Ru1**.

<table><caption>**Table 2.** Outcome of the RCM of DEDAM (**S2**) under various conditions (solvent, temperature, and addition of a Lewis acid) for **Ru1** and **Ru3**.</caption><thead><tr><th>Entry</th><th>[Ru]</th><th>Solvent</th><th>Additive</th><th>Temperature [°C]</th><th>Conversion [%]<sup>a</sup></th></tr></thead><tbody><tr><td>1</td><td rowspan="3">Ru1</td><td>DCM</td><td>—</td><td>RT</td><td>49</td></tr><tr><td>2</td><td>DCM</td><td>B(OEt)<sub>3</sub></td><td>RT</td><td>56</td></tr><tr><td>3</td><td>Toluene</td><td>—</td><td>50</td><td>&gt;99</td></tr><tr><td>4</td><td rowspan="2">Ru3</td><td>DCM</td><td>—</td><td>RT</td><td>79</td></tr><tr><td>5</td><td>Toluene</td><td>—</td><td>50</td><td>&gt;99</td></tr></tbody></table>

## Immobilization of Ru-NHC complexes on Metal-Organic Frameworks

Subsequently, we undertook the task of immobilizing the newly synthesized Ru-NHC complexes onto metal-organic frameworks (MOFs) as heterogeneous supports. For the immobilization of Ru-NHC on MOFs, the more active **Ru3** complex was selected as the candidate for immobilization. Considering the relatively large size of the Hoveyda–Grubbs-type complexes and the stability of a potential solid support, (Al)MIL-101-NH<sub>2</sub> was chosen, which met the aforementioned criteria [24].

<footnote><sup>a</sup> Conversion assessed by GC using dodecane as an internal standard</footnote>
The catalyst **Ru3** (approximately 10 w/w%) was dissolved in DCM or toluene (1 mM), followed by the addition of an appropriate amount of (AI)MIL-101-NH₂. After 1 hour of stirring, the mixture was centrifuged, and the supernatant was examined using spectrophotometric methods to determine the catalyst concentration in the supernatant. In both DCM and toluene, almost quantitative sorption was observed (99.2% and 99.4% of the catalyst was absorbed in (AI)MIL-101-NH₂, respectively). Since the catalyst was held inside the MOF by reversible noncovalent interactions, the desorption was the next step to investigate. To assess the robustness of the catalyst's immobilization, it was washed the obtained Ru3@(AI)MIL-101-NH₂ with toluene and DCM, starting with the less polar toluene. The material was placed on a G4 filtering funnel with a side argon inlet, and solvents were slowly filtered through the catalyst@MOF. The supernatants were monitored using UV-Vis. Interestingly, no significant leaching of the absorbed catalyst from (AI)MIL-101-NH₂ was observed under these challenging dynamic conditions—the total amount of Ru3 washed out with toluene (20 mL) and DCM (20 mL) was less than 10%.

Powder X-ray diffraction (PXRD) studies revealed that the material remained crystalline after catalyst immobilization, but its porosity, expressed as BET surface area, dropped significantly from 1753 m²/g for pristine MOF to 564 m²/g for Ru3@(AI)MIL-101-NH₂.

<figure><img src="image_240.png" /><figcaption>**Scheme 64.** Approach for the immobilization of Ru3 within the structure of (AI)MIL-101-NH₂.</figcaption></figure>

Having successfully immobilized **Ru3** within the structure of (AI)MIL-101-NH₂ and conducted sorption and leaching experiments, the next step was to test the activity of the newly obtained heterogeneous catalyst in metathesis, specifically in the model ring-closing metathesis of compound DEDAM in toluene at 80 °C with 1 mol% of the heterogenized catalyst (refer to Table 3). Based on the leaching experiment, the less polar medium resulted in negligible desorption from the solid support, making toluene a more favorable solvent in this case. In comparison to the homogeneous catalysis discussed earlier, where the conversion was quantitative, the heterogenized system Ru3@(AI)MIL-101-NH₂ demonstrated poorer performance. After 24 hours of reaction, only 54% conversion was achieved under these conditions. Increasing the Ru3@(AI)MIL-101-NH₂ loading up to 2 mol% did not lead to increased conversion.

Next, it was decided to test the new system on a set of olefin metathesis substrates with the standard loading (1 mol%) of Ru3@MOF (Table 4). Surprisingly, excellent results were obtained in the ring-closing metathesis (RCM) reaction of DATA (S3)—the conversion reached 65% in 3 hours and 91% in 24 hours. It should be mentioned here that attempts to improve the catalyst performance by treating
The catalyst **Ru3** (approximately 10 w/w%) was dissolved in DCM or toluene (1 mM), followed by the addition of an appropriate amount of (AI)MIL-101-NH₂. After 1 hour of stirring, the mixture was centrifuged, and the supernatant was examined using spectrophotometric methods to determine the catalyst concentration in the supernatant. In both DCM and toluene, almost quantitative sorption was observed (99.2% and 99.4% of the catalyst was absorbed in (AI)MIL-101-NH₂, respectively). Since the catalyst was held inside the MOF by reversible noncovalent interactions, the desorption was the next step to investigate. To assess the robustness of the catalyst's immobilization, it was washed the obtained Ru3@(AI)MIL-101-NH₂ with toluene and DCM, starting with the less polar toluene. The material was placed on a G4 filtering funnel with a side argon inlet, and solvents were slowly filtered through the catalyst@MOF. The supernatants were monitored using UV-Vis. Interestingly, no significant leaching of the absorbed catalyst from (AI)MIL-101-NH₂ was observed under these challenging dynamic conditions—the total amount of Ru3 washed out with toluene (20 mL) and DCM (20 mL) was less than 10%.

Powder X-ray diffraction (PXRD) studies revealed that the material remained crystalline after catalyst immobilization, but its porosity, expressed as BET surface area, dropped significantly from 1753 m²/g for pristine MOF to 564 m²/g for Ru3@(AI)MIL-101-NH₂.

<figure><img src="image_238.png" /><figcaption>**Scheme 64.** Approach for the immobilization of Ru3 within the structure of (AI)MIL-101-NH₂.</figcaption></figure>

Having successfully immobilized **Ru3** within the structure of (AI)MIL-101-NH₂ and conducted sorption and leaching experiments, the next step was to test the activity of the newly obtained heterogeneous catalyst in metathesis, specifically in the model ring-closing metathesis of compound DEDAM in toluene at 80 °C with 1 mol% of the heterogenized catalyst (refer to Table 3). Based on the leaching experiment, the less polar medium resulted in negligible desorption from the solid support, making toluene a more favorable solvent in this case. In comparison to the homogeneous catalysis discussed earlier, where the conversion was quantitative, the heterogenized system Ru3@(AI)MIL-101-NH₂ demonstrated poorer performance. After 24 hours of reaction, only 54% conversion was achieved under these conditions. Increasing the Ru3@(AI)MIL-101-NH₂ loading up to 2 mol% did not lead to increased conversion.

Next, it was decided to test the new system on a set of olefin metathesis substrates with the standard loading (1 mol%) of Ru3@MOF (Table 4). Surprisingly, excellent results were obtained in the ring-closing metathesis (RCM) reaction of DATA (S3)—the conversion reached 65% in 3 hours and 91% in 24 hours. It should be mentioned here that attempts to improve the catalyst performance by treating
the MOF with dry HCl in Et₂O after sorption of the catalyst were attempted. Interestingly, the conversion of DATA (S3) in the reaction catalyzed with **Ru3@(Al)MIL-101-NH₂·HCl** reached 78% in just 15 minutes, but, unfortunately, did not increase after 24 hours. Disappointingly, the RCM reaction of the olefin metathesis substrates S3 and S4 conducted in a similar manner (1 mol% of **Ru3@(Al)MIL-101-NH₂**) resulted in a poorer outcome, giving only 31% and 30% conversion, respectively.

<table><caption>**Table 3.** Results of the RCM of DEDAM (S2) with **Ru3** (homogeneous) and **Ru33@(Al)MIL-101-NH₂** (heterogeneous) complexes in toluene.</caption><thead><tr><th>Entry</th><th>[Ru]</th><th>Loading [mol%]</th><th>Time [h]</th><th>Conversion [%]<sup>a</sup></th></tr></thead><tbody><tr><td>1</td><td rowspan="2">Ru3</td><td rowspan="2">1.0</td><td>3</td><td>95</td></tr><tr><td>2</td><td>24</td><td>&gt;99</td></tr><tr><td>3</td><td rowspan="4">Ru3@(Al)MIL-101-NH₂</td><td rowspan="2">1.0</td><td>3</td><td>53</td></tr><tr><td>4</td><td>24</td><td>54</td></tr><tr><td>5</td><td rowspan="2">2.0</td><td>3</td><td>50</td></tr><tr><td>6</td><td>24</td><td>51</td></tr></tbody></table>

<table><caption>**Table 4.** Results of the RCM reaction of selected dienes S2-S4 using **Ru38@(Al)MIL-101-NH₂** complex (1 mol%) in toluene at 80 °C.</caption><thead><tr><th rowspan="2">Entry</th><th rowspan="2">[Ru]@MOF</th><th rowspan="2">Substrate</th><th colspan="3">Conversion [%]<sup>a</sup></th></tr><tr><th>At split</th><th>In filtrate (24 h)</th><th>In suspension (24 h)</th></tr></thead><tbody><tr><td>1</td><td>Ru3@(Al)MIL-101-NH₂</td><td>EtO₂C-CO₂Et-S2</td><td>26 (3 h)</td><td>26</td><td>31</td></tr><tr><td>2</td><td>Ru3@(Al)MIL-101-NH₂</td><td>Ph-C6H4-O-S(=O)-N(CH₃)₂S3</td><td>65 (3 h)</td><td>65</td><td>91<sup>b</sup></td></tr><tr><td>3</td><td>Ru3@(Al)MIL-101-NH₂·HCl</td><td>Ph-C6H4-O-S(=O)-N(CH₃)₂S3</td><td>78 (0.25 h)</td><td>78</td><td>78</td></tr><tr><td>4</td><td>Ru3@(Al)MIL-101-NH₂</td><td>Ph-C6H4-O-S(=O)-N(CH₃)₂S4</td><td>13 (3 h)</td><td>14</td><td>30</td></tr></tbody></table>

In summary, two new unsymmetrical N-heterocyclic carbene (uNHC)-based ruthenium complexes featuring a phenolic OH function were successfully obtained and fully characterized. The more active complex was then effectively immobilized on the metal-organic framework (MOF) support. Desorption studies suggest that the highly porous structure of (Al)MIL-101-NH₂ provides a favorable

<footnote><sup>a</sup> Conversion was determined by GC using tetradecane as internal standard.</footnote>

<footnote><sup>a</sup> Conversion was determined by GC using tetradecane as internal standard.</footnote>

<footnote><sup>b</sup> Isolated yield for the compound is 79%.</footnote>
environment for the non-covalent immobilization of a phenol-tagged ruthenium catalyst. After immobilization, the Lewis acidic coordinatively unsaturated centers located inside the well-defined nanoscopic voids in a crystalline framework of the MOF strongly bind the ruthenium complex, resulting in negligible leaching even in polar solvents, such as DCM. The catalytic activity of this formed heterogeneous system was unfortunately lower than the activity of the corresponding homogeneous catalyst in solution; however, it demonstrated catalytic activity in selected olefin metathesis reactions. We believe that the results reported herein represent a valid proof-of-concept and are the very first example of catalyst immobilization through phenol-MOF interactions.

## Attempts on the immobilization of Ru-NHC complexes on dendrimers

Lastly, we embarked on the challenging task of immobilizing Ru-NHC complexes on PPH Janus dendrimers. In this regard, the goal was to obtain the first phosphorus Janus dendrimer applicable in olefin metathesis catalysis, specifically in aqueous media.

To analyze and optimize the reaction conditions for coupling the Ru-NHC complexes and dendrimers, the initial steps were carried out using a model dendrimer molecule, denoted as MDM **27**. MDM was chosen for its structure, which contains a –P(S)Cl₂ group that mimics the surface of typical PPH dendrimers. This characteristic makes MDM an excellent candidate to fine-tune the reaction conditions for the desired coupling. The synthesis of MDM **27** followed the previously reported procedure [25], employing conventional conditions for dendrimer systems (Scheme 10). Specifically, benzaldehyde was subjected to a condensation reaction with *N*-methyldichlorothiophosphorhydrazide (**9**) involving the aldehyde and amino groups, resulting in the formation of **27** as a white solid in 90% yield.

In line with the extensive research conducted by the group of Caminade and Majoral, it has been established that MDM **27** can be tailored similarly to dendrimers. Notably, **27** can undergo reactions with phenols or amines for the substitution of the two chlorides in P–Cl bonds present on its surface.

<figure><img src="image_241.png" /><figcaption>**Scheme 65.** Synthesis of model dendrimer molecule **27**.</figcaption></figure>

The initial attempt to obtain a Ru-NHC@**27** complex involved employing the conventional substitution conditions commonly used for the synthesis of dendrons and dendrimers (illustrated in Scheme 11a). In this process, model **27** was dissolved in dry THF, and Cs₂CO₃ and **Ru1** (in a slight excess) were added. The reaction mixture was stirred at room temperature, and the progression of the reaction was monitored using NMR spectroscopy. Unfortunately, attempts to obtain the desired product through this methodology were unsuccessful displaying decomposition products in the NMR mixtures. Given the preliminary results obtained and considering research conducted by Fogg's group regarding the bimolecular decomposition of olefin metathesis catalysts when they are in close proximity [26,27], it was hypothesized that the di-substitution of **27** to **Ru4** might have occurred, followed by rapid decomposition to form dimeric ruthenium species.
environment for the non-covalent immobilization of a phenol-tagged ruthenium catalyst. After immobilization, the Lewis acidic coordinatively unsaturated centers located inside the well-defined nanoscopic voids in a crystalline framework of the MOF strongly bind the ruthenium complex, resulting in negligible leaching even in polar solvents, such as DCM. The catalytic activity of this formed heterogeneous system was unfortunately lower than the activity of the corresponding homogeneous catalyst in solution; however, it demonstrated catalytic activity in selected olefin metathesis reactions. We believe that the results reported herein represent a valid proof-of-concept and are the very first example of catalyst immobilization through phenol-MOF interactions.

## Attempts on the immobilization of Ru-NHC complexes on dendrimers

Lastly, we embarked on the challenging task of immobilizing Ru-NHC complexes on PPH Janus dendrimers. In this regard, the goal was to obtain the first phosphorus Janus dendrimer applicable in olefin metathesis catalysis, specifically in aqueous media.

To analyze and optimize the reaction conditions for coupling the Ru-NHC complexes and dendrimers, the initial steps were carried out using a model dendrimer molecule, denoted as MDM **27**. MDM was chosen for its structure, which contains a –P(S)Cl₂ group that mimics the surface of typical PPH dendrimers. This characteristic makes MDM an excellent candidate to fine-tune the reaction conditions for the desired coupling. The synthesis of MDM **27** followed the previously reported procedure [25], employing conventional conditions for dendrimer systems (Scheme 10). Specifically, benzaldehyde was subjected to a condensation reaction with *N*-methyldichlorothiophosphorhydrazide (**9**) involving the aldehyde and amino groups, resulting in the formation of **27** as a white solid in 90% yield.

In line with the extensive research conducted by the group of Caminade and Majoral, it has been established that MDM **27** can be tailored similarly to dendrimers. Notably, **27** can undergo reactions with phenols or amines for the substitution of the two chlorides in P–Cl bonds present on its surface.

<figure><img src="image_239.png" /><figcaption>**Scheme 65.** Synthesis of model dendrimer molecule **27**.</figcaption></figure>

The initial attempt to obtain a Ru-NHC@**27** complex involved employing the conventional substitution conditions commonly used for the synthesis of dendrons and dendrimers (illustrated in Scheme 11a). In this process, model **27** was dissolved in dry THF, and Cs₂CO₃ and **Ru1** (in a slight excess) were added. The reaction mixture was stirred at room temperature, and the progression of the reaction was monitored using NMR spectroscopy. Unfortunately, attempts to obtain the desired product through this methodology were unsuccessful displaying decomposition products in the NMR mixtures. Given the preliminary results obtained and considering research conducted by Fogg's group regarding the bimolecular decomposition of olefin metathesis catalysts when they are in close proximity [26,27], it was hypothesized that the di-substitution of **27** to **Ru4** might have occurred, followed by rapid decomposition to form dimeric ruthenium species.
To try to address this issue, the second approach to obtain a Ru@dendrimer structure focused on the asymmetric substitution of **27** (Scheme **11b**). The goal was to incorporate one Ru-complex unit into **27**, resulting in a mono-substituted species **42**, and then react it with a nucleophilic agent to complete the substitution. Model dendrimer **27** was reacted under basic conditions with 1.0 equivalent of **Ru1** to obtain the corresponding mono-substituted species **42**. Subsequently, several nucleophilic agents (**43–45**, known to react with dendrimeric structures) were tested for their ability to react with **42** and complete the substitution.

The formation of intermediate **42** was confirmed by NMR spectroscopy, specifically by the shift of the phosphorus peak in ³¹P{¹H} NMR to 68.5 ppm, typical for mono-substituted **27**-type species. Following the formation of **42**, attempts to introduce the previously mentioned nucleophilic species to produce the fully substituted model dendrimer were made. Unfortunately, despite using various compounds as potential nucleophilic agents (such as phenol, isopropylamine, or 2-methoxyethan-1-amine), none of the attempts resulted in successful formation of the desired Ru@model dendrimer molecules. Analysis of the reaction mixtures indicated that the introduction of such nucleophilic species to form disubstituted compounds was not achieved, and the attempts to isolate any Ru@model dendrimer molecules led to compound degradation.

<figure><img src="image_242.png" /><figcaption>**Scheme 66.** (a) Reaction conditions for the attempt on the synthesis of **Ru39**; (b) Synthetic approaches attempted for the preparation of asymmetrically substituted model dendrimer **156** with one unit of **Ru36**.</figcaption></figure>
To try to address this issue, the second approach to obtain a Ru@dendrimer structure focused on the asymmetric substitution of **27** (Scheme **11b**). The goal was to incorporate one Ru-complex unit into **27**, resulting in a mono-substituted species **42**, and then react it with a nucleophilic agent to complete the substitution. Model dendrimer **27** was reacted under basic conditions with 1.0 equivalent of **Ru1** to obtain the corresponding mono-substituted species **42**. Subsequently, several nucleophilic agents (**43–45**, known to react with dendrimeric structures) were tested for their ability to react with **42** and complete the substitution.

The formation of intermediate **42** was confirmed by NMR spectroscopy, specifically by the shift of the phosphorus peak in ³¹P{¹H} NMR to 68.5 ppm, typical for mono-substituted **27**-type species. Following the formation of **42**, attempts to introduce the previously mentioned nucleophilic species to produce the fully substituted model dendrimer were made. Unfortunately, despite using various compounds as potential nucleophilic agents (such as phenol, isopropylamine, or 2-methoxyethan-1-amine), none of the attempts resulted in successful formation of the desired Ru@model dendrimer molecules. Analysis of the reaction mixtures indicated that the introduction of such nucleophilic species to form disubstituted compounds was not achieved, and the attempts to isolate any Ru@model dendrimer molecules led to compound degradation.

<figure><img src="image_240.png" /><figcaption>**Scheme 66.** (a) Reaction conditions for the attempt on the synthesis of **Ru39**; (b) Synthetic approaches attempted for the preparation of asymmetrically substituted model dendrimer **156** with one unit of **Ru36**.</figcaption></figure>
The final attempt to prepare Ru@dendrimer structures was inspired by a recent development described by Grela's group [28]. In this approach, Ru-NHC complexes were synthesized through the derivatization a ruthenium complex which already contained a primary alcohol tag in the NHC backbone.

Therefore, and by applying a similar approach, the synthesis of a Ru-NHC@dendrimer system involved the reaction of the phenolic Ru-complexes with an acid-terminated model dendrimer. This acid-terminated model dendrimer, denoted as **48**, was synthesized in two steps from **27** (Scheme 12a) by substitution of **27** with tert-butyl 4-hydroxybenzoate and later hydrolysis of the ester.

The synthesis of Ru-NHC@model dendrimer **Ru5** was attempted by combining the approaches developed for the acid-terminated model dendrimer **48** and the acylation reaction of the "phenolic" ruthenium complexes. The process is outlined in Scheme 12b. First, acid-terminated model dendrimer **48** was subjected to oxalyl chloride in DCM at -20 °C to generate the acyl chloride derivative **49**. Subsequently, the acyl chloride **49** solution generated *in situ* was slowly added to a DCM solution of **Ru3**, previously treated with an excess of triethylamine for 1 h. The reaction mixture was stirred for a period ranging from 1 to 16 hours, and its progress was monitored using NMR spectroscopy. The NMR results indicated the presence of two phosphorus species, as evidenced by two singlets at 60.88 ppm and 61.24 ppm, which was consistent with the formation of the desired product as well as a second phosphorus-containing species –either hydrolysis derivatives or decomposition products. However, no successful means of purification led to the isolation of the desired product. The synthesis of Ru-NHC@dendrimer **Ru5** represented a challenging endeavor, with complications arising during the purification process. Further optimization and investigation may be required to successfully obtain the desired product.

<figure><img src="image_243.png" /><figcaption>**Scheme 67.** (a) Synthesis of acid-terminated model dendrimer **162** in two steps from **155**; (b) Attempt on the synthesis of **Ru42** via acylation reaction from **162** and **Ru38**.</figcaption></figure>
The final attempt to prepare Ru@dendrimer structures was inspired by a recent development described by Grela's group [28]. In this approach, Ru-NHC complexes were synthesized through the derivatization a ruthenium complex which already contained a primary alcohol tag in the NHC backbone.

Therefore, and by applying a similar approach, the synthesis of a Ru-NHC@dendrimer system involved the reaction of the phenolic Ru-complexes with an acid-terminated model dendrimer. This acid-terminated model dendrimer, denoted as **48**, was synthesized in two steps from **27** (Scheme 12a) by substitution of **27** with tert-butyl 4-hydroxybenzoate and later hydrolysis of the ester.

The synthesis of Ru-NHC@model dendrimer **Ru5** was attempted by combining the approaches developed for the acid-terminated model dendrimer **48** and the acylation reaction of the "phenolic" ruthenium complexes. The process is outlined in Scheme 12b. First, acid-terminated model dendrimer **48** was subjected to oxalyl chloride in DCM at -20 °C to generate the acyl chloride derivative **49**. Subsequently, the acyl chloride **49** solution generated *in situ* was slowly added to a DCM solution of **Ru3**, previously treated with an excess of triethylamine for 1 h. The reaction mixture was stirred for a period ranging from 1 to 16 hours, and its progress was monitored using NMR spectroscopy. The NMR results indicated the presence of two phosphorus species, as evidenced by two singlets at 60.88 ppm and 61.24 ppm, which was consistent with the formation of the desired product as well as a second phosphorus-containing species –either hydrolysis derivatives or decomposition products. However, no successful means of purification led to the isolation of the desired product. The synthesis of Ru-NHC@dendrimer **Ru5** represented a challenging endeavor, with complications arising during the purification process. Further optimization and investigation may be required to successfully obtain the desired product.

<figure><img src="image_241.png" /><figcaption>**Scheme 67.** (a) Synthesis of acid-terminated model dendrimer **162** in two steps from **155**; (b) Attempt on the synthesis of **Ru42** via acylation reaction from **162** and **Ru38**.</figcaption></figure>
Conclusions

The primary aim of this research has been to advance the field of catalysis by developing novel supported ruthenium complexes. This Thesis has centered on two key objectives: the preparation of PPH Janus dendrimers to facilitate the grafting of Ru-complexes on their surfaces for catalytic applications, and the synthesis of innovative Ru-NHC complexes for olefin metathesis, followed by the immobilization attempts onto dendrimers and MOFs.

In summary, although one of the targeted objectives of this Thesis—immobilization of Ru-NHC complexes on Janus dendrimers—was not achieved, the development of two unprecedented Ru-supported systems for catalysis has been unveiled. Specifically, the **Ru3@MOF** system has been developed, demonstrating that **(Al)MIL-101-NH2** offers a favorable environment for the non-covalent immobilization of a phenol-tagged ruthenium catalyst.

In parallel, the first-ever PPH Janus dendrimer with potential applications in catalysis has been reported. Specifically, **23-Ru@[G1][G1]-PEG** was synthesized, featuring PEG chains on one side of the structure and Ru(*p*-cymene) derivatives on the other side, making it a highly promising material for use in catalysis. The applicability of the Ru@dendrimer **23** in catalysis was tested for the isomerization of 1-octen-3-ol in both THF and biphasic *n*-heptane/water mixtures, demonstrating a positive dendritic effect in both scenarios. Notably, in the biphasic solvent system, only the dendrimeric complex **23-Ru@[G1][G1]-PEG** exhibited activity for the targeted reaction, while monometallic and bimetallic **26** and **29** showed no conversion of **S1** (after 24 h). Furthermore, the recyclability and reusability of the dendrimeric system were assessed, revealing full conversion of **S1** for up to three consecutive runs, with minimal metal contamination in the final product (<0.05%). These findings highlight the potential of dendrimeric catalysts in catalytic applications, particularly for reactions in aqueous or biphasic systems, and underscore the stability and effectiveness of the developed Ru@dendrimer complex.

**1. References**

[1] A. M. Caminade, C. O. Turrin, R. Laurent, A. Ouali, B. Delavaux-Nicot, *Dendrimers: Towards Catalytic, Material and Biomedical Uses*, 1st ed.; John Wiley & Sons Ltd., **2011**. ISBN: 9780470748817.

[2] A. M. Caminade, R. Laurent, *Coord. Chem. Rev.*, **2019**, *389*, 59-72. DOI: [10.1016/j.ccr.2019.03.007](https://doi.org/10.1016/j.ccr.2019.03.007).

[3] E. Badetti, A. M. Caminade, J. P. Majoral, M. Moreno-Mañas, R. M. Sebastián, *Langmuir* **2008**, *24*, 2090-2101. DOI: [10.1021/la7013418](https://doi.org/10.1021/la7013418).

[4] J. N. H. Reek, S. Arévalo, R. van Heerbeek, P. C. J. Kamer, P. W. N. M. van Leeuwen, *Adv. Catal.*, **2006**, *49*, 71-151. DOI: [10.1016/S0360-0564(05)49002-1](https://doi.org/10.1016/S0360-0564(05)49002-1).

[5] J. Cejas-Sánchez, A. Kajetanowicz, K. Grela, A. M. Caminade, R. M. Sebastián, *Molecules* **2023**, *28*, 5570-5588. DOI: [10.3390/molecules28145570](https://doi.org/10.3390/molecules28145570).

[6] C. D. Spicer, M. Pujari-Palmer, H. Autefage, G. Insley, P. Procter, H. Engqvist, M. M. Stevens. *ACS Cent. Sci.*, **2020**, *6*, 226-231. DOI: [10.1021/acscentsci.9b01149](https://doi.org/10.1021/acscentsci.9b01149).

[7] A. Makarem, K. D. Klika, G. Litau, Y. Remde, K. Kopka, *J. Org. Chem.*, **2019**, *84*, 7501-7508. DOI: [10.1021/acs.joc.9b00832](https://doi.org/10.1021/acs.joc.9b00832).

[8] Y. Q. Jiang, K. Wu, Q. Zhang, K. Q. Li, Y. Y. Li, P. Y. Xin, *Chem. Commun.*, **2018**, *54*, 13821-13824. DOI: [10.1039/C8CC08226J](https://doi.org/10.1039/C8CC08226J).

[9] A. Zibarov, A. Oukhrib, J. Aujard Catot, C. O. Turrin, A. M. Caminade, *Molecules* **2021**, *26*, 1-24. DOI: [10.3390/molecules26134017](https://doi.org/10.3390/molecules26134017).

[10] A. M. Caminade, J. P. Majoral, *Molecules* **2016**, *21*, 538-562. DOI: [10.3390/molecules21040538](https://doi.org/10.3390/molecules21040538).

[11] A. Sourdon, M. Gary-Bobo, M. Maynadier, M. Garcia, J. P. Majoral, A. M. Caminade, O. Mongin, M. Blanchard-Desce, *Chem. Eur. J.*, **2019**, *25*, 3637-3649. DOI: [10.1002/chem.201805617](https://doi.org/10.1002/chem.201805617).
Conclusions

The primary aim of this research has been to advance the field of catalysis by developing novel
supported ruthenium complexes. This Thesis has centered on two key objectives: the preparation of
PPH Janus dendrimers to facilitate the grafting of Ru-complexes on their surfaces for catalytic
applications, and the synthesis of innovative Ru-NHC complexes for olefin metathesis, followed by the
immobilization attempts onto dendrimers and MOFs.

In summary, although one of the targeted objectives of this Thesis—immobilization of Ru-NHC complexes on Janus dendrimers—was not achieved, the development of two unprecedented Ru-supported systems for catalysis has been unveiled. Specifically, the **Ru3@MOF** system has been developed, demonstrating that **(Al)MIL-101-NH2** offers a favorable environment for the non-covalent immobilization of a phenol-tagged ruthenium catalyst.

In parallel, the first-ever PPH Janus dendrimer with potential applications in catalysis has been reported. Specifically, **23-Ru@[G₁][G₁]-PEG** was synthesized, featuring PEG chains on one side of the structure and Ru(*p*-cymene) derivatives on the other side, making it a highly promising material for use in catalysis. The applicability of the Ru@dendrimer **23** in catalysis was tested for the isomerization of 1-octen-3-ol in both THF and biphasic *n*-heptane/water mixtures, demonstrating a positive dendritic effect in both scenarios. Notably, in the biphasic solvent system, only the dendrimeric complex **23-Ru@[G₁][G₁]-PEG** exhibited activity for the targeted reaction, while monometallic and bimetallic **26** and **29** showed no conversion of **S1** (after 24 h). Furthermore, the recyclability and reusability of the dendrimeric system were assessed, revealing full conversion of **S1** for up to three consecutive runs, with minimal metal contamination in the final product (<0.05%). These findings highlight the potential of dendrimeric catalysts in catalytic applications, particularly for reactions in aqueous or biphasic systems, and underscore the stability and effectiveness of the developed Ru@dendrimer complex.

**1. References**

[1] A. M. Caminade, C. O. Turrin, R. Laurent, A. Ouali, B. Delavaux-Nicot, *Dendrimers: Towards Catalytic, Material and Biomedical Uses*, 1st ed.; John Wiley & Sons Ltd., **2011**. ISBN: 9780470748817.

[2] A. M. Caminade, R. Laurent, *Coord. Chem. Rev.*, **2019**, *389*, 59–72. DOI: [10.1016/j.ccr.2019.03.007](https://doi.org/10.1016/j.ccr.2019.03.007).

[3] E. Badetti, A. M. Caminade, J. P. Majoral, M. Moreno-Mañas, R. M. Sebastián, *Langmuir* **2008**, *24*, 2090–2101. DOI: [10.1021/la7013418](https://doi.org/10.1021/la7013418).

[4] J. N. H. Reek, S. Arévalo, R. van Heerbeek, P. C. J. Kamer, P. W. N. M. van Leeuwen, *Adv. Catal.*, **2006**, *49*, 71–151. DOI: [10.1016/S0360-0564(05)49002-1](https://doi.org/10.1016/S0360-0564(05)49002-1).

[5] J. Cejas-Sánchez, A. Kajetanowicz, K. Grela, A. M. Caminade, R. M. Sebastián, *Molecules* **2023**, *28*, 5570–5588. DOI: [10.3390/molecules28145570](https://doi.org/10.3390/molecules28145570).

[6] C. D. Spicer, M. Pujari-Palmer, H. Autefage, G. Insley, P. Procter, H. Engqvist, M. M. Stevens. *ACS Cent. Sci.*, **2020**, *6*, 226–231. DOI: [10.1021/acscentsci.9b01149](https://doi.org/10.1021/acscentsci.9b01149).

[7] A. Makarem, K. D. Klika, G. Litau, Y. Remde, K. Kopka, *J. Org. Chem.*, **2019**, *84*, 7501–7508. DOI: [10.1021/acs.joc.9b00832](https://doi.org/10.1021/acs.joc.9b00832).

[8] Y. Q. Jiang, K. Wu, Q. Zhang, K. Q. Li, Y. Y. Li, P. Y. Xin, *Chem. Commun.*, **2018**, *54*, 13821–13824. DOI: [10.1039/C8CC08226J](https://doi.org/10.1039/C8CC08226J).

[9] A. Zibarov, A. Oukhrib, J. Aujard Catot, C. O. Turrin, A. M. Caminade, *Molecules* **2021**, *26*, 1–24. DOI: [10.3390/molecules26134017](https://doi.org/10.3390/molecules26134017).

[10] A. M. Caminade, J. P. Majoral, *Molecules* **2016**, *21*, 538–562. DOI: [10.3390/molecules21040538](https://doi.org/10.3390/molecules21040538).

[11] A. Sourdon, M. Gary-Bobo, M. Maynadier, M. Garcia, J. P. Majoral, A. M. Caminade, O. Mongin, M. Blanchard-Desce, *Chem. Eur. J.*, **2019**, *25*, 3637–3649. DOI: [10.1002/chem.201805617](https://doi.org/10.1002/chem.201805617).
[12] O. Alami, R. Laurent, M. Tassé, Y. Coppel, J. Bignon, S. El Kazzouli, J. P. Majoral, N. El Brahami, A. M. Caminade, *Chem. Eur. J.*, **2023**, *29*, e202302198. DOI: [10.1002/chem.202302198](https://doi.org/10.1002/chem.202302198).

[13] L. Biancalana, L. K. Batchelor, A. De Palo, S. Zacchini, G. Pampaloni, P. J. Dyson, F. A. Marchetti, *Dalton Trans.*, **2017**, *46*, 12001–12004. DOI: [10.1039/C7DT02062G](https://doi.org/10.1039/C7DT02062G).

[14] I. Angurell, C. O. Turrin, R. Laurent, V. Maraval, P. Servin, O. Rossell, M. Seco, A. M. Caminade, J. P. Majoral, *J. Organomet. Chem.*, **2007**, *692*, 1928–1939. DOI: [10.1016/j.jorganchem.2007.01.001](https://doi.org/10.1016/j.jorganchem.2007.01.001).

[15] L. P. Wu, M. Ficker, J. B. Christensen, P. N. Trohopoulos, S. M. Moghimi, *Bioconjug. Chem.*, **2015**, *26*, 1198–1211. DOI: [10.1021/acs.bioconjchem.5b00031](https://doi.org/10.1021/acs.bioconjchem.5b00031).

[16] C. O. Turrin, V. Maraval, J. Leclaire, E. Dantras, C. Lacabanne, A. M. Caminade, J. P. Majoral, *Tetrahedron* **2003**, *59*, 3965–3973. DOI: [10.1016/S0040-4020(03)00465-4](https://doi.org/10.1016/S0040-4020(03)00465-4).

[17] P. Servin, R. Laurent, L. Gonsalvi, M. Tristany, M. Peruzzini, J. P. Majoral, A. M. Caminade, *Dalton Trans.*, **2009**, 4432–4434. DOI: [10.1039/B906393P](https://doi.org/10.1039/B906393P).

[18] J. E. Bäckvall, U. Andreasson, *Tetrahedron Lett.*, **1993**, *34*, 5459–5462. DOI: [10.1016/S0040-4039(00)73934-7](https://doi.org/10.1016/S0040-4039(00)73934-7).

[19] K. Grela, *Olefin Metathesis: Theory and Practice*; Grela, K., Ed.; Wiley: Hobboken, **2014**. ISBN: 9781118711613. DOI: [10.1002/9781118711613](https://doi.org/10.1002/9781118711613).

[20] A. Fürstner, L. Ackermann, B. Gabor, R. Goddard, C. W. Lehmann, R. Mynott, F. Stelzer, O. R. Thiel, *Chem. Eur. J.*, **2001**, *7*, 3236–3253. DOI: [10.1002/1521-3765(20010803)7:15<3236::AID-CHEM3236>3.0.CO;2-S](https://doi.org/10.1002/1521-3765(20010803)7:15<3236::AID-CHEM3236>3.0.CO;2-S).

[21] M. Nadirova, J. Cejas-Sánchez, R. M. Sebastián, M. Wiszniewski, M. J. Chmielewski, A. Kajetanowicz, K. Grela, *Catalysts* **2023**, *13*, 297–309. DOI: [10.3390/catal13020297](https://doi.org/10.3390/catal13020297).

[22] M. Patrzyłek, J. Piątkowski, A. Kajetanowicz, K. Grela, *Synlett* **2019**, *30*, 1981–1987. DOI: [10.1055/s-0037-1611834](https://doi.org/10.1055/s-0037-1611834).

[23] P. Małecki, K. Gajda, R. Gajda, K. Woźniak, B. Trzaskowski, A. Kajetanowicz, K. Grela, *Organometallics* **2017**, *36*, 2153–2166. DOI: [10.1021/acs.organomet.7b00211](https://doi.org/10.1021/acs.organomet.7b00211).

[24] P. Serra-Crespo, E. V. Ramos-Fernandez, J. Gascon, F. Kapteijn, *Chem. Mater.*, **2011**, *23*, 2565–2572. DOI: [10.1021/cm103644b](https://doi.org/10.1021/cm103644b).

[25] G. Franc, E. Badetti, C. Duhayon, Y. Coppel, C. O. Turrin, J. P. Majoral, R. M. Sebastián, A. M. Caminade, *New J. Chem.*, **2010**, *34*, 547–555. DOI: [10.1039/B9NJ00568D](https://doi.org/10.1039/B9NJ00568D).

[26] D. L. Nascimento, M. Foscato, G. Occhipinti, V. R. Jensen, D. E. Fogg, *J. Am. Chem. Soc.*, **2021**, *143*, 11072–11079. DOI: [10.1021/jacs.1c04424](https://doi.org/10.1021/jacs.1c04424).

[27] G. A. Bailey, M. Foscato, C. S. Higman, C. S. Day, V. R. Jensen, D. E. Fogg, D. E. *J. Am. Chem. Soc.*, **2018**, *140*, 6931–6944. DOI: [10.1021/jacs.8b02709](https://doi.org/10.1021/jacs.8b02709).

[28] L. Monsigny, S. J. Czarnocki, M. Sienkiewicz, W. Kopcha, R. Frankfurter, C. Vogt, W. Solodenko, A. Kajetanowicz, A. Kirschning, K. Grela, *Eur. J. Org. Chem.*, **2021**, *46*, 6424–6434. DOI: [10.1002/ejoc.202101092](https://doi.org/10.1002/ejoc.202101092).
[12] O. Alami, R. Laurent, M. Tassé, Y. Coppel, J. Bignon, S. El Kazzouli, J. P. Majoral, N. El Brahami, A. M. Caminade, *Chem. Eur. J.*, **2023**, *29*, e202302198. DOI: [10.1002/chem.202302198](https://doi.org/10.1002/chem.202302198).

[13] L. Biancalana, L. K. Batchelor, A. De Palo, S. Zacchini, G. Pampaloni, P. J. Dyson, F. A. Marchetti, *Dalton Trans.*, **2017**, *46*, 12001–12004. DOI: [10.1039/C7DT02062G](https://doi.org/10.1039/C7DT02062G).

[14] I. Angurell, C. O. Turrin, R. Laurent, V. Maraval, P. Servin, O. Rossell, M. Seco, A. M. Caminade, J. P. Majoral, *J. Organomet. Chem.*, **2007**, *692*, 1928–1939. DOI: [10.1016/j.jorganchem.2007.01.001](https://doi.org/10.1016/j.jorganchem.2007.01.001).

[15] L. P. Wu, M. Ficker, J. B. Christensen, P. N. Trohopoulos, S. M. Moghimi, *Bioconjug. Chem.*, **2015**, *26*, 1198–1211. DOI: [10.1021/acs.bioconjchem.5b00031](https://doi.org/10.1021/acs.bioconjchem.5b00031).

[16] C. O. Turrin, V. Maraval, J. Leclaire, E. Dantras, C. Lacabanne, A. M. Caminade, J. P. Majoral, *Tetrahedron* **2003**, *59*, 3965–3973. DOI: [10.1016/S0040-4020(03)00465-4](https://doi.org/10.1016/S0040-4020(03)00465-4).

[17] P. Servin, R. Laurent, L. Gonsalvi, M. Tristany, M. Peruzzini, J. P. Majoral, A. M. Caminade, *Dalton Trans.*, **2009**, 4432–4434. DOI: [10.1039/B906393P](https://doi.org/10.1039/B906393P).

[18] J. E. Bäckvall, U. Andreasson, *Tetrahedron Lett.*, **1993**, *34*, 5459–5462. DOI: [10.1016/S0040-4039(00)73934-7](https://doi.org/10.1016/S0040-4039(00)73934-7).

[19] K. Grela, *Olefin Metathesis: Theory and Practice*; Grela, K., Ed.; Wiley: Hobboken, **2014**. ISBN: 9781118711613. DOI: [10.1002/9781118711613](https://doi.org/10.1002/9781118711613).

[20] A. Fürstner, L. Ackermann, B. Gabor, R. Goddard, C. W. Lehmann, R. Mynott, F. Stelzer, O. R. Thiel, *Chem. Eur. J.*, **2001**, *7*, 3236–3253. DOI: [10.1002/1521-3765(20010803)7:15<3236::AID-CHEM3236>3.0.CO;2-S](https://doi.org/10.1002/1521-3765(20010803)7:15<3236::AID-CHEM3236>3.0.CO;2-S).

[21] M. Nadirova, J. Cejas-Sánchez, R. M. Sebastián, M. Wiszniewski, M. J. Chmielewski, A. Kajetanowicz, K. Grela, *Catalysts* **2023**, *13*, 297–309. DOI: [10.3390/catal13020297](https://doi.org/10.3390/catal13020297).

[22] M. Patrzyłek, J. Piątkowski, A. Kajetanowicz, K. Grela, *Synlett* **2019**, *30*, 1981–1987. DOI: [10.1055/s-0037-1611834](https://doi.org/10.1055/s-0037-1611834).

[23] P. Małecki, K. Gajda, R. Gajda, K. Woźniak, B. Trzaskowski, A. Kajetanowicz, K. Grela, *Organometallics* **2017**, *36*, 2153–2166. DOI: [10.1021/acs.organomet.7b00211](https://doi.org/10.1021/acs.organomet.7b00211).

[24] P. Serra-Crespo, E. V. Ramos-Fernandez, J. Gascon, F. Kapteijn, *Chem. Mater.*, **2011**, *23*, 2565–2572. DOI: [10.1021/cm103644b](https://doi.org/10.1021/cm103644b).

[25] G. Franc, E. Badetti, C. Duhayon, Y. Coppel, C. O. Turrin, J. P. Majoral, R. M. Sebastián, A. M. Caminade, *New J. Chem.*, **2010**, *34*, 547–555. DOI: [10.1039/B9NJ00568D](https://doi.org/10.1039/B9NJ00568D).

[26] D. L. Nascimento, M. Foscato, G. Occhipinti, V. R. Jensen, D. E. Fogg, *J. Am. Chem. Soc.*, **2021**, *143*, 11072–11079. DOI: [10.1021/jacs.1c04424](https://doi.org/10.1021/jacs.1c04424).

[27] G. A. Bailey, M. Foscato, C. S. Higman, C. S. Day, V. R. Jensen, D. E. Fogg, D. E. *J. Am. Chem. Soc.*, **2018**, *140*, 6931–6944. DOI: [10.1021/jacs.8b02709](https://doi.org/10.1021/jacs.8b02709).

[28] L. Monsigny, S. J. Czarnocki, M. Sienkiewicz, W. Kopcha, R. Frankfurter, C. Vogt, W. Solodenko, A. Kajetanowicz, A. Kirschning, K. Grela, *Eur. J. Org. Chem.*, **2021**, *46*, 6424–6434. DOI: [10.1002/ejoc.202101092](https://doi.org/10.1002/ejoc.202101092).
Deepthy KRISHNAN

ESR11

**Thesis co-directors**

Prof. Anders Riisager Danmarks Tekniske Universitet, Lyngby, Denmark

Dr. Karine Philippot Laboratoire de Chimie de Coordination, Toulouse, France

Dr. M. Rosa Axet

**Thesis defense**

Department of Chemistry, Danmarks Tekniske Universitet, 28 November 2023
Deepthy KRISHNAN

ESR11

**Thesis co-directors**

Prof. Anders Riisager Danmarks Tekniske Universitet, Lyngby, Denmark

Dr. Karine Philippot Laboratoire de Chimie de Coordination, Toulouse, France

Dr. M. Rosa Axet

**Thesis defense**

Department of Chemistry, Danmarks Tekniske Universitet, 28 November 2023
<figure><img src="image_244.png" /></figure>
<figure><img src="image_242.png" /></figure>
# Mono- and Bimetallic Nanoparticles Stabilized by Functionalized Ionic Liquids: Synthesis and Catalytic Applications

## Ionic Liquids

The most practical definition of an ionic liquid (IL) is 'a liquid composed entirely of ions' [1]. There are diverse salts which are liquids at ambient temperature. ILs that are liquid at room temperature are called room temperature ionic liquids (RTILs). Most ILs are composed of a large organic cation of low symmetry, and a much smaller inorganic polyatomic anion with the charge highly delocalized. The liquid state is favored by small lattice enthalpy and large entropy changes, attributed to the large size and conformational flexibility of the two weakly coordinating ions [2]. While the structural arrangement of IL resembles that of a salt, the main difference is that the coulombic interactions between the ions in a salt is much stronger than in ILs as the result of the similarity between the size and nature of the ions, giving them a strong crystalline structure with relative high melting point, e.g. the melting point of NaCl is 801 °C [3]. ILs exhibit notably distinct physical characteristics which includes negligible vapor pressure, high charge density, high polarity, high dielectric constant, and capability to form supramolecular networks [4]. These properties can be designed through combination of various cations and anions as presented hereafter. The cationic center of an IL involves typically a positively charged nitrogen, phosphorus or sulfur atom. Those described thus far involve mainly ammonium, sulphonium, imidazolium, pyridinium, pyrrolidinium, phosphonium, oxazolium, etc. cations substituted with alkyl chains. Anions of ILs are usually organic or inorganic weakly basic compounds with a delocalized negative charge [5].

## Task-specific ionic liquids

Task-specific ionic liquids (TSIL) can be defined as ILs which incorporate a covalently linked reactive functionality [6]. The functional group (FG) like carboxylic acid (-COOH) [7], amine (-NR₃) [8] or nitrile (-CN) [9] can be incorporated either into the anion or cationic part or both [10]. Such functionalities can impart additional properties to the ILs that can be thus employed for specific tasks, with several objectives. For instance, ILs with appended amines have been developed to favor the separation of CO₂ from gas stream via carbamate formation [11]. ILs modified with a hydroxyl group (-OH) have been used as a phase transfer catalyst for ethoxybenzene synthesis [12]. Metal-ligating groups incorporated into ILs can be used for metal-ion extraction from aqueous solution [13]. The physicochemical properties of these TSILs like solubility in molecular solvents, thermal stability and chemical properties like reactivity, depend on the nature of the functional groups incorporated [14]. A TSIL can be a RTIL with covalently attached FG that can act not only as a reaction medium but also as a reagent/catalyst. A TSIL can also be a binary system of functionalized salts, which may be solid at room temperature that can be dissolved in a conventional IL [15]. ILs have emerged as versatile components that can act both as solvent and stabilizers for the synthesis of metal nanoparticles (NPs), providing an efficient synthesis method. For instance, Guleria and coworkers used an imidazolium-based RTIL as a solvent, reducing and stabilizing agent to synthesize stable α-Se NPs (d_m = 34 nm) exhibiting antioxidant properties [16]. On a similar note, Garg et al. reported the synthesis of palladium NPs (d_m = 1.4 and 1.7 nm) by employing a choline-based IL [17]. These IL-stabilized Pd NPs exhibited notable catalytic efficiency in hydrogenation reactions of substrates with various functional groups.
# Mono- and Bimetallic Nanoparticles Stabilized by Functionalized Ionic Liquids: Synthesis and Catalytic Applications

## Ionic Liquids

The most practical definition of an ionic liquid (IL) is 'a liquid composed entirely of ions' [1]. There are diverse salts which are liquids at ambient temperature. ILs that are liquid at room temperature are called room temperature ionic liquids (RTILs). Most ILs are composed of a large organic cation of low symmetry, and a much smaller inorganic polyatomic anion with the charge highly delocalized. The liquid state is favored by small lattice enthalpy and large entropy changes, attributed to the large size and conformational flexibility of the two weakly coordinating ions [2]. While the structural arrangement of IL resembles that of a salt, the main difference is that the coulombic interactions between the ions in a salt is much stronger than in ILs as the result of the similarity between the size and nature of the ions, giving them a strong crystalline structure with relative high melting point, e.g. the melting point of NaCl is 801 °C [3]. ILs exhibit notably distinct physical characteristics which includes negligible vapor pressure, high charge density, high polarity, high dielectric constant, and capability to form supramolecular networks [4]. These properties can be designed through combination of various cations and anions as presented hereafter. The cationic center of an IL involves typically a positively charged nitrogen, phosphorus or sulfur atom. Those described thus far involve mainly ammonium, sulphonium, imidazolium, pyridinium, pyrrolidinium, phosphonium, oxazolium, etc. cations substituted with alkyl chains. Anions of ILs are usually organic or inorganic weakly basic compounds with a delocalized negative charge [5].

## Task-specific ionic liquids

Task-specific ionic liquids (TSIL) can be defined as ILs which incorporate a covalently linked reactive functionality [6]. The functional group (FG) like carboxylic acid (-COOH) [7], amine (-NR₃) [8] or nitrile (-CN) [9] can be incorporated either into the anion or cationic part or both [10]. Such functionalities can impart additional properties to the ILs that can be thus employed for specific tasks, with several objectives. For instance, ILs with appended amines have been developed to favor the separation of CO₂ from gas stream via carbamate formation [11]. ILs modified with a hydroxyl group (-OH) have been used as a phase transfer catalyst for ethoxybenzene synthesis [12]. Metal-ligating groups incorporated into ILs can be used for metal-ion extraction from aqueous solution [13]. The physicochemical properties of these TSILs like solubility in molecular solvents, thermal stability and chemical properties like reactivity, depend on the nature of the functional groups incorporated [14]. A TSIL can be a RTIL with covalently attached FG that can act not only as a reaction medium but also as a reagent/catalyst. A TSIL can also be a binary system of functionalized salts, which may be solid at room temperature that can be dissolved in a conventional IL [15]. ILs have emerged as versatile components that can act both as solvent and stabilizers for the synthesis of metal nanoparticles (NPs), providing an efficient synthesis method. For instance, Guleria and coworkers used an imidazolium-based RTIL as a solvent, reducing and stabilizing agent to synthesize stable α-Se NPs (d_m = 34 nm) exhibiting antioxidant properties [16]. On a similar note, Garg et al. reported the synthesis of palladium NPs (d_m = 1.4 and 1.7 nm) by employing a choline-based IL [17]. These IL-stabilized Pd NPs exhibited notable catalytic efficiency in hydrogenation reactions of substrates with various functional groups.
Thus, previous results show that ILs can be employed for the synthesis of metal NPs. ILs possesses intriguing physical and chemical properties and presents the advantage to act both as stabilizer and solvent in the reaction, resulting in reduced utilization of chemicals and limited waste, which diminishes the environmental footprint. Careful tailoring of imidazolium based ILs with functional groups has proven a relevant way to improve catalytic performance of metal NPs.

## Metal nanoparticles

Nanotechnology is a scientific discipline that deals with the preparation and use of nano-size particles within the size range of 1 to 100 nm. The term 'nanoparticle' originates from the Greek word 'nano,' meaning 'small' and, when used as a prefix, denotes a size of 10⁻⁹ meter (= 1 nm) [18]. Metal nanoparticles (NPs) including transition metal NPs find versatile applications in various fields like molecular biology, medicine, physics, organic and inorganic chemistry, and material science [19,20]. Decreasing particle size to the nanoscale imparts unique and enhanced characteristics like morphology and particle size distribution, which are not exhibited by larger bulk materials [21]. Electronic properties of metal NPs are situated at the frontier between molecular species and bulk compounds [22]. Their surface-to-volume ratio is significantly higher than that of larger particles or atoms, leading to a high number of potential active sites on the surface [23]. This unique extrinsic property of the surface area of NPs contributes to them being highly attractive and influences also various intrinsic properties, including their strong surface reactivity which is size-dependent [24]. The properties observed at the nanoscale are mainly due to two key factors:

1. **Quantum size effect** [25]: In bulk metals, the electronic behavior is characterized by the presence of energy bands. The valence band contains the valence electrons, typically s- and d-electrons in the case of transition metals. The conduction band of metals partially overlaps with the valence band and hence is partially occupied by electrons responsible for the electrical conductivity of metals. In semiconductors the valence and conduction bands are separated by a specific energy gap, which is considerably larger in insulators. When a metal particle undergoes continuous size reduction the bands turn into discrete energy levels. At this stage, the bulk properties of the metal disappear and are substituted by "quantum dot," which are governed by the principles of quantum mechanics. Such confinement of charge carriers within a small space, resulting in discrete energy levels, is referred to as the "quantum size effect." It brings changes in the electronic properties of metals in NPs.

2. **Surface/interface effect** [26,27]: Metal NPs offer a higher number of potential active sites compared to bulk catalytic materials due to their high surface-to-volume ratio making them highly attractive as catalysts. Furthermore, the diverse shapes, crystallographic facets and different fractions of surface atoms located at their corners and edges can contribute to their versatility in catalytic applications.

An organometallic approach is generally employed for the synthesis of metal NPs. In this synthetic approach, metal-organic complexes (metal precursors) with zero or low oxidation state of the metal are decomposed at mild reaction conditions in the presence of carefully chosen ligands (Scheme 1). Olefinic complexes are preferred as hydrogenation of such complexes results in the reduction of the unsaturated ligands within their coordination sphere into their corresponding alkanes, which are inert towards the metallic surface [28]. For example, (1,5-cyclooctadiene)(1,3,5,7-cyclooctatetraene)ruthenium, [Ru(COD)(COT)], is easily decomposed under hydrogen (1-3 bar) at
Thus, previous results show that ILs can be employed for the synthesis of metal NPs. ILs possesses intriguing physical and chemical properties and presents the advantage to act both as stabilizer and solvent in the reaction, resulting in reduced utilization of chemicals and limited waste, which diminishes the environmental footprint. Careful tailoring of imidazolium based ILs with functional groups has proven a relevant way to improve catalytic performance of metal NPs.

## Metal nanoparticles

Nanotechnology is a scientific discipline that deals with the preparation and use of nano-size particles within the size range of 1 to 100 nm. The term 'nanoparticle' originates from the Greek word 'nano,' meaning 'small' and, when used as a prefix, denotes a size of 10⁻⁹ meter (= 1 nm) [18]. Metal nanoparticles (NPs) including transition metal NPs find versatile applications in various fields like molecular biology, medicine, physics, organic and inorganic chemistry, and material science [19,20]. Decreasing particle size to the nanoscale imparts unique and enhanced characteristics like morphology and particle size distribution, which are not exhibited by larger bulk materials [21]. Electronic properties of metal NPs are situated at the frontier between molecular species and bulk compounds [22]. Their surface-to-volume ratio is significantly higher than that of larger particles or atoms, leading to a high number of potential active sites on the surface [23]. This unique extrinsic property of the surface area of NPs contributes to them being highly attractive and influences also various intrinsic properties, including their strong surface reactivity which is size-dependent [24]. The properties observed at the nanoscale are mainly due to two key factors:

1) **Quantum size effect** [25]: In bulk metals, the electronic behavior is characterized by the presence of energy bands. The valence band contains the valence electrons, typically s- and d-electrons in the case of transition metals. The conduction band of metals partially overlaps with the valence band and hence is partially occupied by electrons responsible for the electrical conductivity of metals. In semiconductors the valence and conduction bands are separated by a specific energy gap, which is considerably larger in insulators. When a metal particle undergoes continuous size reduction the bands turn into discrete energy levels. At this stage, the bulk properties of the metal disappear and are substituted by "quantum dot," which are governed by the principles of quantum mechanics. Such confinement of charge carriers within a small space, resulting in discrete energy levels, is referred to as the "quantum size effect." It brings changes in the electronic properties of metals in NPs.

2) **Surface/interface effect** [26,27]: Metal NPs offer a higher number of potential active sites compared to bulk catalytic materials due to their high surface-to-volume ratio making them highly attractive as catalysts. Furthermore, the diverse shapes, crystallographic facets and different fractions of surface atoms located at their corners and edges can contribute to their versatility in catalytic applications.

An organometallic approach is generally employed for the synthesis of metal NPs. In this synthetic approach, metal-organic complexes (metal precursors) with zero or low oxidation state of the metal are decomposed at mild reaction conditions in the presence of carefully chosen ligands (Scheme 1). Olefinic complexes are preferred as hydrogenation of such complexes results in the reduction of the unsaturated ligands within their coordination sphere into their corresponding alkanes, which are inert towards the metallic surface [28]. For example, (1,5-cyclooctadiene)(1,3,5,7-cyclooctatetraene)ruthenium, [Ru(COD)(COT)], is easily decomposed under hydrogen (1-3 bar) at
room temperature [29], bis(1,5-cyclooctadiene)nickel, $[Ni(COD)_2]$ can be employed for the preparation of Ni NPs [30] and tetraallyldirhenium(II), $[Re_2(C_3H_5)_4]$, allowed to get pure Re NPs [31]. All these precursors generate byproducts like propane and cyclooctane which are inert to the metal surface and can be removed under vacuum. The stabilizing agent introduced at the beginning of the reaction plays a crucial role, as it governs the characteristics of the resulting nanostructures [28]. Some of the stabilizers include simple ligands such as alcohols [32], thiols [33], silanes [34], aminoalcohols [35], 3-aminopropyltriethoxysilane [36], amines [33], diphosphines [37] and ILs [38] as well as polymers [39] can also be used. Through this method, a wide variety of metal nanostructures can be obtained by adjusting the choice of metals, reaction conditions, and stabilizing agents.

<figure><img src="image_245.png" /><figcaption>**Scheme 1.** Schematic representation for the synthesis of metal nanoparticles (NPs) by the organometallic approach adapted from [28].</figcaption></figure>

The organometallic approach for the synthesis of metal NPs provides numerous advantages, which are primarily centered around the precise control of the reaction conditions (which in-turn affect the surface of the particles) and the control over particle characteristics (size, size distribution and shape). Such control allows to obtain monodispersed NPs with desired properties. One potential challenge lies in the synthesis and handling of organometallic complexes that require inert conditions. Nevertheless, the advantages gained in terms of controlling the characteristics of NPs make the efforts involved justifiable. Indeed, having well-controlled metal NPs allow to finely investigate their properties for applications in different domains, including catalysis among others.

## Objectives and outlook

The main objectives of the thesis include:

1) The synthesis and characterization of ILs and functionalized ILs (FILs).

2) Utilization of the synthesized ILs for synthesis of transition metal NPs mainly employing ruthenium, nickel and rhenium. Complete characterization of these metal NPs/ILs systems through state of art techniques including TEM, TGA, XPS, NMR, ATR-IR etc.

3) Employment of the series of metal NPs/ILs systems in catalytic hydrogenation of substrates like styrene, cinnamyl alcohol, 2,3-benzofuran, trans-2-hexen-1-al, hexanal, benzonitrile, benzylamine, phenylacetylene and $(R)-(+)-limonene to study the activity and reactivity of such systems.
room temperature [29], bis(1,5-cyclooctadiene)nickel, $[Ni(COD)_2]$ can be employed for the preparation of Ni NPs [30] and tetraallyldirhenium(II), $[Re_2(C_3H_5)_4]$, allowed to get pure Re NPs [31]. All these precursors generate byproducts like propane and cyclooctane which are inert to the metal surface and can be removed under vacuum. The stabilizing agent introduced at the beginning of the reaction plays a crucial role, as it governs the characteristics of the resulting nanostructures [28]. Some of the stabilizers include simple ligands such as alcohols [32], thiols [33], silanes [34], aminoalcohols [35], 3-aminopropyltriethoxysilane [36], amines [33], diphosphines [37] and ILs [38] as well as polymers [39] can also be used. Through this method, a wide variety of metal nanostructures can be obtained by adjusting the choice of metals, reaction conditions, and stabilizing agents.

<figure><img src="image_243.png" /><figcaption>**Scheme 1.** Schematic representation for the synthesis of metal nanoparticles (NPs) by the organometallic approach adapted from [28].</figcaption></figure>

The organometallic approach for the synthesis of metal NPs provides numerous advantages, which are primarily centered around the precise control of the reaction conditions (which in-turn affect the surface of the particles) and the control over particle characteristics (size, size distribution and shape). Such control allows to obtain monodispersed NPs with desired properties. One potential challenge lies in the synthesis and handling of organometallic complexes that require inert conditions. Nevertheless, the advantages gained in terms of controlling the characteristics of NPs make the efforts involved justifiable. Indeed, having well-controlled metal NPs allow to finely investigate their properties for applications in different domains, including catalysis among others.

## Objectives and outlook

The main objectives of the thesis include:

1) The synthesis and characterization of ILs and functionalized ILs (FILs).

2) Utilization of the synthesized ILs for synthesis of transition metal NPs mainly employing ruthenium, nickel and rhenium. Complete characterization of these metal NPs/ILs systems through state of art techniques including TEM, TGA, XPS, NMR, ATR-IR etc.

3) Employment of the series of metal NPs/ILs systems in catalytic hydrogenation of substrates like styrene, cinnamyl alcohol, 2,3-benzofuran, trans-2-hexen-1-al, hexanal, benzonitrile, benzylamine, phenylacetylene and $(R)-(+)-limonene to study the activity and reactivity of such systems.
The first part focuses on synthesizing task-specific (TS) ILs, namely MEM (1-methoxyethoxymethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide) and MME (1-methoxymethoxyethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide) (Table 1). This choice is inspired by the literature data evidence that methoxy functionality can lead to well dispersed and highly active metal NPs for catalysis. Numerous examples can be found in the literature of metal NPs that have been synthesized using polyethylene glycol (PEG) as stabilizer and that have shown high catalytic activity in several reactions. For instance, Pd NPs stabilized by PEG demonstrated remarkable catalytic activity and recyclability towards styrene and nitrobenzene hydrogenation under mild reaction conditions. The formed Pd NPs were well dispersed and had an average diameter of 4 nm [40]. As another non-exhaustive example, Sun and coworkers synthesized homogeneously distributed PEG-stabilized Rh NPs of 1.7 nm in size by simple reduction of $RhCl_3 \cdot 3H_2O$ under hydrogen. The formed Rh NPs were found as a highly efficient and recyclable catalyst for the hydroformylation of olefins [41].

<table><caption>**Table 1.** Structure of synthesized imidazolium based ILs.</caption><thead><tr><th>Ionic liquid</th><th>Structure</th></tr></thead><tbody><tr><td>H</td><td><img src="image_0_0.png" alt="Chemical structure of an ionic liquid with a N<sub>2</sub>N<sup>+</sup> anion and a C<sub>6</sub>H<sub>5</sub>-COO<sup>-</sup> anion"></td></tr><tr><td>MEM</td><td><img src="image_0_1.png" alt="Chemical structure of an ionic liquid with a N<sub>2</sub>N<sup>+</sup> anion, a C<sub>6</sub>H<sub>5</sub>-COO<sup>-</sup> anion, and a C<sub>6</sub>H<sub>5</sub>-O<sup>-</sup> anion"></td></tr><tr><td>MME</td><td><img src="image_0_2.png" alt="Chemical structure of an ionic liquid with a N<sub>2</sub>N<sup>+</sup> anion, a C<sub>6</sub>H<sub>5</sub>-COO<sup>-</sup> anion, and a C<sub>6</sub>H<sub>5</sub>-O<sup>-</sup> anion"></td></tr><tr><td>CN</td><td><img src="image_0_3.png" alt="Chemical structure of an ionic liquid with a N<sub>2</sub>N<sup>+</sup> anion, a C<sub>6</sub>H<sub>5</sub>-COO<sup>-</sup> anion, and a CN<sup>-</sup> anion"></td></tr></tbody></table>

Various characterizations of the ILs have been performed, this includes ATR-IR Infrared (IR) spectroscopy analysis, Thermal gravimetry (TG) and differential scanning calorimetry (DSC) analyses, Elemental analysis (EA), X-ray photoelectron spectroscopy (XPS) analysis, NMR and Small angle X-ray scattering (SAXS) analysis. Two of the analysis have been provided in detail below:

### a) ATR-IR analysis

Infrared (IR) spectroscopy is one of the most established and standard technique to characterize ILs [42–44]. This technique allows to identify the functional groups present. Vibrational studies of ILs with imidazolium as cation have been widely discussed in literature [45,46]. The region of high frequencies ranging from 2800 to 3200 cm⁻¹ displays a composite arrangement of overlapping bands that are specific to various stretching modes of C-H bonds. Within the range of 800 to 1600 cm⁻¹, distinct bands that correspond to the vibrations of the imidazolium ring can be observed. The range of 400 to 800 cm⁻¹ also encompasses ring vibrations [47]. The stretching frequency of [NTf₂]⁻ anion ranges between 400 – 2000 cm⁻¹ [48]. Figure 1 depicts the IR analyses of the ILs H, MEM, MME, and CN. The bands at 1050, 1180, 1346 cm⁻¹ can be assigned to the stretching frequencies of SN, $CF_3$, $SO_2$, respectively, in [NTf₂]⁻. The bands at 1099 and 1098 cm⁻¹ correspond to the C-O stretching of MEM and MME, respectively. The CN stretching can be seen at 2248 cm⁻¹. The bands at the high frequency region 2800 to 3200 cm⁻¹ correspond to the C-H bonds of the imidazolium cation. The absence of O-H stretching mode of water in the range 3400–3800 cm⁻¹ confirmed the high purity of all the ILs.
<figure><img src="image_246.png" /><figcaption>Figure 1. ATR-IR spectra of ILs.</figcaption></figure>

b) SAXS analysis

Small angle X-ray scattering (SAXS) analysis was performed on all the ILs in collaboration with Prof. John Slattery and Dr. Naomi Elstone at University of York, UK to study the nature of cation-cation, anion-anion, and cation-anion ordering (Figure 2). Two primary diffraction peaks can be observed in the ranges $q \approx 8-9$ nm⁻¹ (peak II) and $q \approx 12.9$ (peak III). The q-value is called the scattering vector and is a function of the scattering angle:

$$q = \frac{4\pi\sin\theta}{\lambda}, 2\theta \text{ is the angle of deflection}$$

For H, one additional peak at $q \approx 2-4$ nm⁻¹ can also be seen. Previous studies of imidazolium ILs with different anions have observed similar diffraction features [49–51]. Peak I depends strongly on the alkyl chain length and reflects on the structural heterogeneity on the nanometer scale of the ILs. Peak II at ~8.8 nm⁻¹, which is commonly called the "charge-ordering peak" (COP) is interpreted as relating to correlations between like charges (anion-anion and cation-cation separations) [52]. Comparing the ILs, the order of intensity of the peak is as follows MME > MEM ~ CN > H which can be seen by plotting the intensity of the peaks against the different. Peak III at ~13.5 nm⁻¹ is commonly referred to as the "contact peak" (CP). The CP is interpreted as relating to correlations between ions of opposite charges i.e., the typical separation of the anions and cations [53]. The ILs follow the same intensity order as peak II.

A series of four imidazolium based ILs, one non-functionalized and three functionalized, namely H, MEM, MME, and CN, were synthesized in good yields by using the standard quaternization and anion exchange reaction synthesis procedure. A complete characterization including IR, TG, DSC, NMR, XPS and SAXS analyses was performed for all synthesized ILs. IR analysis allowed to establish the stretching frequency and the different functional groups of both the anion and the cation (CN, CO, SO₂, CF₃, etc.) thus confirming the identity of each IL. TG and DSC analyses gave information on the thermal behavior of the ILs. They were found to be thermally stable above 200°C for MEM and MME and 450°C in the case of H and CN. The binding energies ($E_b$) of the elements present in each IL were obtained through XPS analysis. The purity of the ILs was evaluated from the NMR analysis. The presence of the
<figure><img src="image_244.png" /><figcaption>Figure 1. ATR-IR spectra of ILs.</figcaption></figure>

b) SAXS analysis

Small angle X-ray scattering (SAXS) analysis was performed on all the ILs in collaboration with Prof. John Slattery and Dr. Naomi Elstone at University of York, UK to study the nature of cation-cation, anion-anion, and cation-anion ordering (Figure 2). Two primary diffraction peaks can be observed in the ranges $q \approx 8-9 \text{ nm}^{-1}$ (peak II) and $q \approx 12.9$ (peak III). The q-value is called the scattering vector and is a function of the scattering angle:

$$q = \frac{4\pi\sin\theta}{\lambda}, 2\theta \text{ is the angle of deflection}$$

For H, one additional peak at $q \approx 2-4 \text{ nm}^{-1}$ can also be seen. Previous studies of imidazolium ILs with different anions have observed similar diffraction features [49–51]. Peak I depends strongly on the alkyl chain length and reflects on the structural heterogeneity on the nanometer scale of the ILs. Peak II at ~8.8 nm⁻¹, which is commonly called the "charge-ordering peak" (COP) is interpreted as relating to correlations between like charges (anion-anion and cation-cation separations) [52]. Comparing the ILs, the order of intensity of the peak is as follows MME > MEM ~ CN > H which can be seen by plotting the intensity of the peaks against the different. Peak III at ~13.5 nm⁻¹ is commonly referred to as the "contact peak" (CP). The CP is interpreted as relating to correlations between ions of opposite charges i.e., the typical separation of the anions and cations [53]. The ILs follow the same intensity order as peak II.

A series of four imidazolium based ILs, one non-functionalized and three functionalized, namely H, MEM, MME, and CN, were synthesized in good yields by using the standard quaternization and anion exchange reaction synthesis procedure. A complete characterization including IR, TG, DSC, NMR, XPS and SAXS analyses was performed for all synthesized ILs. IR analysis allowed to establish the stretching frequency and the different functional groups of both the anion and the cation (CN, CO, SO₂, CF₃, etc.) thus confirming the identity of each IL. TG and DSC analyses gave information on the thermal behavior of the ILs. They were found to be thermally stable above 200°C for MEM and MME and 450°C in the case of H and CN. The binding energies ($E_b$) of the elements present in each IL were obtained through XPS analysis. The purity of the ILs was evaluated from the NMR analysis. The presence of the
characteristic ¹H and ¹³C NMR peaks also contributed confirming the structure of the ILs. The interactions and ordering of the cations and anions of the ILs were studied using SAXS technique. These synthesized and fully characterized ILs have been then used for the stabilization of transition metal NPs of Ru and Ni. The IL was also tested for the synthesis of Ru-Re bimetallic NPs.

<figure><img src="image_247.png" /><figcaption>**Figure 2.** X-ray diffraction patterns for the series of ILs.</figcaption></figure>

The synthesis and characterization of Ru NPs stabilized by two ether-FILs, 1-methoxyethoxymethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [MEMIm][NTf₂] or MEM, and 1-methoxymethoxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide, [MMEIm][NTf₂] or MME are reported following the organometallic approach. The novel Ru/FILs NPs systems (Ru/MEM and Ru/MME) were applied for hydrogenation of styrene and phenylacetylene to probe the surface reactivity of the Ru NPs. In particular, the influence of the ether functions on the catalytic performance was studied and compared to two counterpart catalytic systems based on Ru NPs stabilized by the non-functionalized IL 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Ru/H) and the cyano-FIL [(CH₃CH₂CH₂CH₂CN)MIm][NTf₂] (Ru/CN), respectively. The obtained results evidenced a clear influence of the FIL on the hydrogenation selectivity of the Ru NPs between vinyl and aromatic hydrogenation of styrene, thus demonstrating the key role of the FIL in the catalytic systems of [Ru(COD)(COT)] in the ILs was achieved in 24 h. Ru/ILs NPs systems were then synthesized by introducing 3 bar H₂ to the Fischer-Porter reactor containing the homogeneous mixture at room temperature except for the nitrile-FIL (CN), where complete decomposition of the Ru complex required a higher temperature of 60 °C (Scheme 2). During a period of 22 h, the color of the reaction turbid mixture was observed to change from yellow to black which indicated the decomposition of the Ru complex. The metal content of each batch of Ru/ILs NPs was established by ICP analysis and found to be close to the expected value of 0.2 wt.% Ru (Table 2).

<figure><img src="image_248.png" /><figcaption>**Scheme 2.** Synthesis of Ru/FILs NPs.</figcaption></figure>

<caption>**Table 2.** Metal content of the Ru/FILs NPs and mean size of the formed Ru NPs.</caption>
characteristic ¹H and ¹³C NMR peaks also contributed confirming the structure of the ILs. The interactions and ordering of the cations and anions of the ILs were studied using SAXS technique. These synthesized and fully characterized ILs have been then used for the stabilization of transition metal NPs of Ru and Ni. The IL was also tested for the synthesis of Ru-Re bimetallic NPs.

<figure><img src="image_245.png" /><figcaption>**Figure 2.** X-ray diffraction patterns for the series of ILs.</figcaption></figure>

The synthesis and characterization of Ru NPs stabilized by two ether-FILs, 1-methoxyethoxymethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [MEMIm][NTf₂] or MEM, and 1-methoxymethoxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide, [MMEIm][NTf₂] or MME are reported following the organometallic approach. The novel Ru/FILs NPs systems (Ru/MEM and Ru/MME) were applied for hydrogenation of styrene and phenylacetylene to probe the surface reactivity of the Ru NPs. In particular, the influence of the ether functions on the catalytic performance was studied and compared to two counterpart catalytic systems based on Ru NPs stabilized by the non-functionalized IL 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Ru/H) and the cyano-FIL [(CH₃CH₂CH₂CH₂CN)MIm][NTf₂] (Ru/CN), respectively. The obtained results evidenced a clear influence of the FIL on the hydrogenation selectivity of the Ru NPs between vinyl and aromatic hydrogenation of styrene, thus demonstrating the key role of the FIL in the catalytic systems of [Ru(COD)(COT)] in the ILs was achieved in 24 h. Ru/ILs NPs systems were then synthesized by introducing 3 bar H₂ to the Fischer-Porter reactor containing the homogeneous mixture at room temperature except for the nitrile-FIL (CN), where complete decomposition of the Ru complex required a higher temperature of 60 °C (Scheme 2). During a period of 22 h, the color of the reaction turbid mixture was observed to change from yellow to black which indicated the decomposition of the Ru complex. The metal content of each batch of Ru/ILs NPs was established by ICP analysis and found to be close to the expected value of 0.2 wt.% Ru (Table 2).

<figure><img src="image_246.png" /><figcaption>**Scheme 2.** Synthesis of Ru/FILs NPs.</figcaption></figure>

<caption>**Table 2.** Metal content of the Ru/FILs NPs and mean size of the formed Ru NPs.</caption>
<table><thead><tr><th>Ru/FILs NPs</th><th>Ionic liquid</th><th>Ru content (wt.%) <sup>a</sup></th><th>Ru NP mean size with standard deviation (nm) <sup>b</sup></th></tr></thead><tbody><tr><td>Ru/H</td><td><img src="image_0_0.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.16</td><td>1.5 ± 0.8</td></tr><tr><td>Ru/MEM</td><td><img src="image_0_1.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.20</td><td>2.2 ± 0.3</td></tr><tr><td>Ru/MME</td><td><img src="image_0_2.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.17</td><td>1.3 ± 0.1</td></tr><tr><td>Ru/CN</td><td><img src="image_0_3.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.20</td><td>1.3 ± 0.2</td></tr></tbody></table>

XPS, TGA, NMR and TEM analyses were performed on the catalytic systems to fully characterize them. The TEM images of the Ru/FILs systems are provided in Figure 4.

<figure><img src="image_249.png" /><figcaption>**Figure 4.** TEM images of Ru/FILs NPs with their corresponding size distribution (scale bar = 100 nm).</figcaption></figure>

<footnote><sup>a</sup> Determined by ICP analyses. <sup>b</sup> Determined from analyses of TEM images.</footnote>
<table><thead><tr><th>Ru/FILs NPs</th><th>Ionic liquid</th><th>Ru content (wt.%) <sup>a</sup></th><th>Ru NP mean size with standard deviation (nm) <sup>b</sup></th></tr></thead><tbody><tr><td>Ru/H</td><td><img src="image_0_0.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.16</td><td>1.5 ± 0.8</td></tr><tr><td>Ru/MEM</td><td><img src="image_0_1.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.20</td><td>2.2 ± 0.3</td></tr><tr><td>Ru/MME</td><td><img src="image_0_2.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.17</td><td>1.3 ± 0.1</td></tr><tr><td>Ru/CN</td><td><img src="image_0_3.png" alt="Chemical structure of N<sub>2</sub>N<sub>2</sub>[NTf<sub>2</sub>]</img></td><td>0.20</td><td>1.3 ± 0.2</td></tr></tbody></table>

XPS, TGA, NMR and TEM analyses were performed on the catalytic systems to fully characterize them. The TEM images of the Ru/FILs systems are provided in Figure 4.

<figure><img src="image_247.png" /><figcaption>**Figure 4.** TEM images of Ru/FILs NPs with their corresponding size distribution (scale bar = 100 nm).</figcaption></figure>

<footnote><sup>a</sup> Determined by ICP analyses. <sup>b</sup> Determined from analyses of TEM images.</footnote>
## Catalysis with Ru/ILs

The catalytic performances of the Ru/ILs NP systems were investigated for the hydrogenation of styrene (S) to form ethylbenzene (EB) and ethylcyclohexane (ECH) using mild reaction conditions (30 °C, 5 bar H₂, S:Ru ratio 200:1) and vigorous stirring (1500 rpm) to avoid mass transfer issues during reaction with the moderately viscous IL phases (Scheme 3). Table 3 summarizes the catalytic results obtained. Note that the IL alone did not show any conversion of S when submitted to the same reaction conditions.

<figure><img src="image_250.png" /><figcaption>**Scheme 3.** Hydrogenation of styrene (S) to ethyl benzene (EB) and ethyl cyclohexane (ECH).</figcaption></figure>

<table><caption>**Table 3.** Hydrogenation of (S) with Ru/FILs NPs catalysts. <sup>a</sup></caption><thead><tr><th rowspan="2">Catalyst system</th><th rowspan="2">Time (h)</th><th rowspan="2">Conversion (%)<sup>b</sup></th><th colspan="2">Selectivity (%)<sup>b</sup></th></tr><tr><th>EB</th><th>ECH</th></tr></thead><tbody><tr><td>Ru/H</td><td>0.5</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/H</td><td>24</td><td>&gt;99</td><td>93</td><td>7</td></tr><tr><td>Ru/MEM</td><td>1</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/MEM</td><td>24</td><td>&gt;99</td><td>78</td><td>22</td></tr><tr><td>Ru/MME</td><td>1.5</td><td>98</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/MME</td><td>24</td><td>98</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/CN</td><td>6</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/CN</td><td>24</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr></tbody></table>

As shown in Table 3, all the Ru/FILs NPs systems were active for the catalytic hydrogenation of S providing full substrate conversion in short reaction times (0.5-6 h). Importantly, the IL alone did not show any conversion of S when submitted to the same reaction conditions (results not shown). The highest TOF value (1,332 h⁻¹) was reached with the Ru NPs embedded in the non-functionalized IL, namely Ru/H catalyst. The two methoxy-functionalized IL systems (Ru/MEM and Ru/MME) yielded high rates (TOFs of 629 h⁻¹ and 212 h⁻¹, respectively), while the Ru/CN had the lowest activity (TOF of 10 h⁻¹). The differences observed in terms of reaction rates may be correlated to the variation in polarity of the IL that can influence the solubility of the substrate, as styrene is expected being more soluble in non-polar domains than in polar ones. In line with this, the H IL that contains only alkyl chains in its structure presents the larger non-polar domains of the IL series [54] and interestingly, the Ru NPs stabilized in this IL led to the highest TOF. Oppositely, the more polar IL is expected to be the CN FIL and the CN-stabilized Ru NPs displayed the lower activity. The recyclability of each Ru/IL NP catalyst was tested in five successive catalytic runs at partial conversion. The obtained results are shown in Figure 5. Notably, the styrene conversion with the Ru/H catalytic system decreased gradually during the five catalytic runs, whereas the catalytic systems with the three FILs maintained similar styrene conversions upon reuse. ICP

<footnote><sup>a</sup> Reaction conditions: 0.02 mmol of Ru, 4 mmol of styrene, 0.3 mmol of octane (internal standard), 5 bar H₂, 30 °C, 1500 rpm. <sup>b</sup> Determined by GC using internal standard technique.</footnote>
## Catalysis with Ru/ILs

The catalytic performances of the Ru/ILs NP systems were investigated for the hydrogenation of styrene (S) to form ethylbenzene (EB) and ethylcyclohexane (ECH) using mild reaction conditions (30 °C, 5 bar H₂, S:Ru ratio 200:1) and vigorous stirring (1500 rpm) to avoid mass transfer issues during reaction with the moderately viscous IL phases (Scheme 3). Table 3 summarizes the catalytic results obtained. Note that the IL alone did not show any conversion of S when submitted to the same reaction conditions.

<figure><img src="image_248.png" /><figcaption>**Scheme 3.** Hydrogenation of styrene (S) to ethyl benzene (EB) and ethyl cyclohexane (ECH).</figcaption></figure>

<table><caption>**Table 3.** Hydrogenation of (S) with Ru/FILs NPs catalysts. <sup>a</sup></caption><thead><tr><th rowspan="2">Catalyst system</th><th rowspan="2">Time (h)</th><th rowspan="2">Conversion (%)<sup>b</sup></th><th colspan="2">Selectivity (%)<sup>b</sup></th></tr><tr><th>EB</th><th>ECH</th></tr></thead><tbody><tr><td>Ru/H</td><td>0.5</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/H</td><td>24</td><td>&gt;99</td><td>93</td><td>7</td></tr><tr><td>Ru/MEM</td><td>1</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/MEM</td><td>24</td><td>&gt;99</td><td>78</td><td>22</td></tr><tr><td>Ru/MME</td><td>1.5</td><td>98</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/MME</td><td>24</td><td>98</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/CN</td><td>6</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr><tr><td>Ru/CN</td><td>24</td><td>&gt;99</td><td>&gt;99</td><td>0</td></tr></tbody></table>

As shown in Table 3, all the Ru/FILs NPs systems were active for the catalytic hydrogenation of S providing full substrate conversion in short reaction times (0.5-6 h). Importantly, the IL alone did not show any conversion of S when submitted to the same reaction conditions (results not shown). The highest TOF value (1,332 h⁻¹) was reached with the Ru NPs embedded in the non-functionalized IL, namely Ru/H catalyst. The two methoxy-functionalized IL systems (Ru/MEM and Ru/MME) yielded high rates (TOFs of 629 h⁻¹ and 212 h⁻¹, respectively), while the Ru/CN had the lowest activity (TOF of 10 h⁻¹). The differences observed in terms of reaction rates may be correlated to the variation in polarity of the IL that can influence the solubility of the substrate, as styrene is expected being more soluble in non-polar domains than in polar ones. In line with this, the H IL that contains only alkyl chains in its structure presents the larger non-polar domains of the IL series [54] and interestingly, the Ru NPs stabilized in this IL led to the highest TOF. Oppositely, the more polar IL is expected to be the CN FIL and the CN-stabilized Ru NPs displayed the lower activity. The recyclability of each Ru/IL NP catalyst was tested in five successive catalytic runs at partial conversion. The obtained results are shown in Figure 5. Notably, the styrene conversion with the Ru/H catalytic system decreased gradually during the five catalytic runs, whereas the catalytic systems with the three FILs maintained similar styrene conversions upon reuse. ICP

<footnote><sup>a</sup> Reaction conditions: 0.02 mmol of Ru, 4 mmol of styrene, 0.3 mmol of octane (internal standard), 5 bar H₂, 30 °C, 1500 rpm. <sup>b</sup> Determined by GC using internal standard technique.</footnote>
analysis of the Ru/H phase from the first run to the fifth one showed a decrease in the Ru content from 0.2 to ~0.1 wt.%, thus confirming that Ru leaching from the IL phase during catalyst recycling was responsible for the lower conversion. In contrast, the Ru content remained essentially unchanged during the five catalytic runs with the Ru/MEM, Ru/MME and Ru/CN systems, which could indicate that Ru-FIL interactions improved the confinement of the Ru NPs in these systems compared to the Ru/H system and that the functionalization of IL had a positive influence on the stability of the catalysts [55]. Interestingly, TEM images of the spent Ru/IL catalysts showed no noticeable change in the mean size nor size distribution of the Ru NPs compared to the pristine systems, pointing out that the Ru NPs remained stable under the reaction conditions for all the systems and leaching was not related to Ru NPs instability. Hence, more likely, the larger non-polar domains in the unfunctionalized IL compared to the FILs enhanced the catalyst solubility in the non-polar washing solvent (pentane), thus leading to a gradual catalyst loss during the intermediate washings between the catalytic runs.

<figure><img src="image_251.png" /><figcaption>**Figure 5.** Recyclability tests of the Ru/FILs NPs catalysts in the hydrogenation of styrene performed at partial conversion: a) H (15 min), b) MEM (30 min), c) MME (30 min) and (d) CN (60 min). Reaction conditions: 0.02 mmol of Ru, 4 mmol of styrene, 0.3 mmol of octane (internal standard), 5 bar H₂, 30 °C, 1500 rpm.</figcaption></figure>

Thus, a series of catalytic systems based on Ru NPs in a non-functionalized IL (H) and three FILs containing cyano (CN) and methoxy (MEM and MME) groups, have been synthesized, characterized, and applied for the hydrogenation of styrene. The methoxy-functionalized systems, Ru/MEM NPs and Ru/MME NPs were novel systems whereas the Ru/H and Ru/CN were reference systems previously described in literature. The collection of systems allowed to study the influence of the nature of the IL on the catalytic properties of the Ru NP catalysts. All the Ru/IL NPs were found to be efficient catalysts for the hydrogenation of styrene under mild reaction conditions (30 °C, 5 bar of H₂), providing full conversion of styrene with full ethyl benzene selectivity in short reaction times (0.5-6 h). Interestingly, a clear difference in activity (TOFs) was observed as a function of the nature of the IL, following the order Ru/H (1,332 h⁻¹) > Ru/MEM (629 h⁻¹) > Ru/MME (212 h⁻¹) >> Ru/CN (10 h⁻¹). In addition, a total selectivity for ethyl benzene was also observed at longer reaction time (24 h) for the Ru/MME and
analysis of the Ru/H phase from the first run to the fifth one showed a decrease in the Ru content from 0.2 to ~0.1 wt.%, thus confirming that Ru leaching from the IL phase during catalyst recycling was responsible for the lower conversion. In contrast, the Ru content remained essentially unchanged during the five catalytic runs with the Ru/MEM, Ru/MME and Ru/CN systems, which could indicate that Ru-FIL interactions improved the confinement of the Ru NPs in these systems compared to the Ru/H system and that the functionalization of IL had a positive influence on the stability of the catalysts [55]. Interestingly, TEM images of the spent Ru/IL catalysts showed no noticeable change in the mean size nor size distribution of the Ru NPs compared to the pristine systems, pointing out that the Ru NPs remained stable under the reaction conditions for all the systems and leaching was not related to Ru NPs instability. Hence, more likely, the larger non-polar domains in the unfunctionalized IL compared to the FILs enhanced the catalyst solubility in the non-polar washing solvent (pentane), thus leading to a gradual catalyst loss during the intermediate washings between the catalytic runs.

<figure><img src="image_249.png" /><figcaption>**Figure 5.** Recyclability tests of the Ru/FILs NPs catalysts in the hydrogenation of styrene performed at partial conversion: a) H (15 min), b) MEM (30 min), c) MME (30 min) and (d) CN (60 min). Reaction conditions: 0.02 mmol of Ru, 4 mmol of styrene, 0.3 mmol of octane (internal standard), 5 bar H₂, 30 °C, 1500 rpm.</figcaption></figure>

Thus, a series of catalytic systems based on Ru NPs in a non-functionalized IL (H) and three FILs containing cyano (CN) and methoxy (MEM and MME) groups, have been synthesized, characterized, and applied for the hydrogenation of styrene. The methoxy-functionalized systems, Ru/MEM NPs and Ru/MME NPs were novel systems whereas the Ru/H and Ru/CN were reference systems previously described in literature. The collection of systems allowed to study the influence of the nature of the IL on the catalytic properties of the Ru NP catalysts. All the Ru/IL NPs were found to be efficient catalysts for the hydrogenation of styrene under mild reaction conditions (30 °C, 5 bar of H₂), providing full conversion of styrene with full ethyl benzene selectivity in short reaction times (0.5-6 h). Interestingly, a clear difference in activity (TOFs) was observed as a function of the nature of the IL, following the order Ru/H (1,332 h⁻¹) > Ru/MEM (629 h⁻¹) > Ru/MME (212 h⁻¹) >> Ru/CN (10 h⁻¹). In addition, a total selectivity for ethyl benzene was also observed at longer reaction time (24 h) for the Ru/MME and
Ru/CN systems, while some successive hydrogenation to ethyl cyclohexane occurred for Ru/H (7%) and Ru/MEM (22%) after 24 h. This shows that the Ru/ILs NPs had a strong preference towards hydrogenation of the vinyl group instead of the aromatic ring under the applied reaction conditions, which is a reactivity pattern different from typically reported for Ru NPs. Accordingly, this indicates that less Ru surface was accessible in Ru/MEM and Ru/CN than in Ru/H and Ru/MEM, which can be attributed partly to lower Ru NP sizes in the former catalysts, though a contributing effect may also derive from metal-IL interactions of the MME and CN FILs *via* -O-CH₂-O- and -CN groups, respectively. Such interactions may, by steric and/or electronic reasons, influence the surface properties of the Ru/ILs NPs and hamper the hydrogenation of the aromatic ring. This hypothesis is supported by the XPS results which evidenced for all Ru/ILs NPs systems a bonding energy of Ru⁰ lower than literature values for metallic Ru, indicating that the Ru NPs and the ILs closely interact. Finally, recycling of the Ru/ILs NPs systems in five catalytic runs evidenced that the FIL-stabilized catalysts were more stable than the non-functionalized Ru/H catalyst system, where Ru leaching likely occurred due to higher solubility of the Ru/H NPs in the workup solvent of the reaction mixture between catalytic runs. Nevertheless, the results show that the functionalization of IL had a positive influence on the stability of the catalysts. In perspective, the work introduces a benign and facile co-solvent free synthesis protocol to obtain well-dispersed and narrow-sized Ru NPs stabilized by FILs containing methoxy-functionalities, which present a good balance between stability and catalytic activity. This allows Ru/ILs NPs to hydrogenate styrene with activity and total selectivity towards ethylbenzene at milder reaction conditions (5 bar H₂, 30 °C) than previously reported in literature [56,57].

Then novel Ni NPs and Ni-NiO NPs stabilized by two ether-FILs, 1-methoxyethoxy-methyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [MEMIm][NTf₂] or MEM, and 1-methoxymethoxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [MMEIm][NTf₂] or MME, were synthesized by the organometallic approach using [Ni(COD)₂] as Ni precursor, and characterized. The Ni/FIL NPs systems (Ni/MEM and Ni/MME) were then applied in the hydrogenation of α,β-unsaturated carbonyl compounds with the aim to probe the surface reactivity in terms of conversion and selectivity. Ni NPs in the non-functionalized IL 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Ni/H) and the cyano-FIL 1-butylcyano-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [(CH₃CH₂CH₂CH₂CN)MIm][NTf₂] (Ni/CN) were also prepared for the purpose of comparison. In a second stage, the as-synthesized Ni NPs were exposed to air which led to Ni-NiO NPs. Hydrogenation of several substrates using these oxidized NPs, including cinnamaldehyde and 2-cyclohexen-1-one among others, was performed to understand the effect of the NP oxidation on the catalytic performance.

The synthesis of Ni NPs was performed at 40-45 °C, using a co-solvent (pentane) to dissolve the lipophilic Ni precursor in the IL, leading to the targeted Ni NPs. Thus, based on this work, the Ni NPs were here synthesized with few modifications of the procedure. [Ni(COD)₂] precursor was dissolved in pentane/IL mixture (1/3 mL) in a Fischer-Porter bottle and the reaction was allowed to proceed for 24 h at 80 °C and 1500 rpm using a magnetic stirrer (Scheme 4). Upon completion of the reaction, a black colloidal suspension was obtained for the four ILs tested, indicating the successful decomposition of the precursor under these optimized conditions. The generated cyclooctane and the solvent were removed under vacuum (~0.05 mbar) overnight. The metal content of each batch of Ni/IL was established by ICP analysis and found to be close to the expected value of 0.10 wt.% Ni (Table 4).
Ru/CN systems, while some successive hydrogenation to ethyl cyclohexane occurred for Ru/H (7%) and Ru/MEM (22%) after 24 h. This shows that the Ru/ILs NPs had a strong preference towards hydrogenation of the vinyl group instead of the aromatic ring under the applied reaction conditions, which is a reactivity pattern different from typically reported for Ru NPs. Accordingly, this indicates that less Ru surface was accessible in Ru/MEM and Ru/CN than in Ru/H and Ru/MEM, which can be attributed partly to lower Ru NP sizes in the former catalysts, though a contributing effect may also derive from metal-IL interactions of the MME and CN FILs *via* -O-CH₂-O- and -CN groups, respectively. Such interactions may, by steric and/or electronic reasons, influence the surface properties of the Ru/ILs NPs and hamper the hydrogenation of the aromatic ring. This hypothesis is supported by the XPS results which evidenced for all Ru/ILs NPs systems a bonding energy of Ru⁰ lower than literature values for metallic Ru, indicating that the Ru NPs and the ILs closely interact. Finally, recycling of the Ru/ILs NPs systems in five catalytic runs evidenced that the FIL-stabilized catalysts were more stable than the non-functionalized Ru/H catalyst system, where Ru leaching likely occurred due to higher solubility of the Ru/H NPs in the workup solvent of the reaction mixture between catalytic runs. Nevertheless, the results show that the functionalization of IL had a positive influence on the stability of the catalysts. In perspective, the work introduces a benign and facile co-solvent free synthesis protocol to obtain well-dispersed and narrow-sized Ru NPs stabilized by FILs containing methoxy-functionalities, which present a good balance between stability and catalytic activity. This allows Ru/ILs NPs to hydrogenate styrene with activity and total selectivity towards ethylbenzene at milder reaction conditions (5 bar H₂, 30 °C) than previously reported in literature [56,57].

Then novel Ni NPs and Ni-NiO NPs stabilized by two ether-FILs, 1-methoxyethoxy-methyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [MEMIm][NTf₂] or MEM, and 1-methoxymethoxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [MMEIm][NTf₂] or MME, were synthesized by the organometallic approach using [Ni(COD)₂] as Ni precursor, and characterized. The Ni/FIL NPs systems (Ni/MEM and Ni/MME) were then applied in the hydrogenation of α,β-unsaturated carbonyl compounds with the aim to probe the surface reactivity in terms of conversion and selectivity. Ni NPs in the non-functionalized IL 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Ni/H) and the cyano-FIL 1-butylcyano-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [(CH₃CH₂CH₂CH₂CN)MIm][NTf₂] (Ni/CN) were also prepared for the purpose of comparison. In a second stage, the as-synthesized Ni NPs were exposed to air which led to Ni-NiO NPs. Hydrogenation of several substrates using these oxidized NPs, including cinnamaldehyde and 2-cyclohexen-1-one among others, was performed to understand the effect of the NP oxidation on the catalytic performance.

The synthesis of Ni NPs was performed at 40-45 °C, using a co-solvent (pentane) to dissolve the lipophilic Ni precursor in the IL, leading to the targeted Ni NPs. Thus, based on this work, the Ni NPs were here synthesized with few modifications of the procedure. [Ni(COD)₂] precursor was dissolved in pentane/IL mixture (1/3 mL) in a Fischer-Porter bottle and the reaction was allowed to proceed for 24 h at 80 °C and 1500 rpm using a magnetic stirrer (Scheme 4). Upon completion of the reaction, a black colloidal suspension was obtained for the four ILs tested, indicating the successful decomposition of the precursor under these optimized conditions. The generated cyclooctane and the solvent were removed under vacuum (~0.05 mbar) overnight. The metal content of each batch of Ni/IL was established by ICP analysis and found to be close to the expected value of 0.10 wt.% Ni (Table 4).
<figure><img src="image_252.png" /><figcaption>**Scheme 4.** Optimized synthesis of Ni/FILs.</figcaption></figure>

<table><caption>**Table 4.** Ni content in Ni/FILs systems and Ni NP mean size.</caption><thead><tr><th>Ni/FIL</th><th>Ionic liquid</th><th>Ni content (wt.%) <sup>a</sup></th><th>Ni NP mean size (nm) <sup>b</sup></th></tr></thead><tbody><tr><td>Ni/H</td><td></td><td>0.11</td><td>5.6 ± 0.3</td></tr><tr><td>Ni/MEM</td><td></td><td>0.12</td><td>4.4 ± 0.4</td></tr><tr><td>Ni/MME</td><td></td><td>0.11</td><td>6.5 ± 0.3</td></tr><tr><td>Ni/CN</td><td></td><td>0.11</td><td>2.8 ± 0.3</td></tr></tbody></table>

XPS, TGA, NMR and TEM analyses were performed on the catalytic systems to fully characterize them. The TEM images of the Ni/FILs systems are provided in Figure 6.

<figure><img src="image_253.png" /><figcaption>**Figure 6.** TEM images of Ni/FILs with their corresponding size distributions (scale bar = 100 nm).</figcaption></figure>

<footnote><sup>a</sup> Determined by ICP analyses. <sup>b</sup> Determined from TEM analyses.</footnote>
<figure><img src="image_250.png" /><figcaption>**Scheme 4.** Optimized synthesis of Ni/FILs.</figcaption></figure>

<table><caption>**Table 4.** Ni content in Ni/FILs systems and Ni NP mean size.</caption><thead><tr><th>Ni/FIL</th><th>Ionic liquid</th><th>Ni content (wt.%) <sup>a</sup></th><th>Ni NP mean size (nm) <sup>b</sup></th></tr></thead><tbody><tr><td>Ni/H</td><td></td><td>0.11</td><td>5.6 ± 0.3</td></tr><tr><td>Ni/MEM</td><td></td><td>0.12</td><td>4.4 ± 0.4</td></tr><tr><td>Ni/MME</td><td></td><td>0.11</td><td>6.5 ± 0.3</td></tr><tr><td>Ni/CN</td><td></td><td>0.11</td><td>2.8 ± 0.3</td></tr></tbody></table>

XPS, TGA, NMR and TEM analyses were performed on the catalytic systems to fully characterize them. The TEM images of the Ni/FILs systems are provided in Figure 6.

<figure><img src="image_251.png" /><figcaption>**Figure 6.** TEM images of Ni/FILs with their corresponding size distributions (scale bar = 100 nm).</figcaption></figure>

<footnote><sup>a</sup> Determined by ICP analyses. <sup>b</sup> Determined from TEM analyses.</footnote>