# Rhodacycles Activity in P-Directed Rhodium-Catalyzed Synthesis of π-Extended Aromatic Fluoranthenyl Phosphines

Charline Sire, Anthonia Tsivery, Henri Sabbadin, Hélène Cattey, Marie-José

Penouilh, Paul Fleurat-Lessard, Jean-cyrille Hierso, Julien Roger

► To cite this version:

Charline Sire, Anthonia Tsivery, Henri Sabbadin, Hélène Cattey, Marie-José Penouilh, et al.. Rhodacycles Activity in P-Directed Rhodium-Catalyzed Synthesis of π-Extended Aromatic Fluoranthenyl Phosphines. European Journal of Inorganic Chemistry, 2025, 28 (8), 10.1002/ejic.202400721. hal-05020655

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# Rhodacycles Activity in P-Directed Rhodium-Catalyzed Synthesis of π-Extended Aromatic Fluoranthenyl Phosphines

Charline Sire,[a] Anthonia Tsivery,[a] Henri Sabbadin,[a] Hélène Cattey,*[a] Marie-José Penouilh, Paul Fleurat-Lessard,[a] Jean-Cyrille Hierso*[a] and Julien Roger*[a]

[a] C. Sire, A. Tsivery, H. Sabbadin, Dr. H. Cattey, M.-J. Penouilh, Prof Dr. P. Fleurat-Lessard, Prof. Dr. J.-C. Hierso, Dr. J. Roger
Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB - UMR CNRS 6302)
Université Bourgogne Europe
9 avenue Alain Savary, 21078 Dijon Cedex, France
E-mail: julien.roger@ube.fr; Jean-Cyrille.Hierso@ube.fr; Helene.Cattey@ube.fr

**Abstract:** We report herein novel polyarylated phosphine diphenylphosphino-1-fluoranthenyl ligands by rhodium-catalyzed phosphine-directed C–H arylation. The nature of the rhodium precatalysts that is employed plays an essential role for the control of the reaction and its resulting product. By using the dimeric [Rh(III)Cl₂Cp*]₂ as the catalyst, a “classical” single peri-functionalization of the polycyclic aromatic hydrocarbons phosphine selectively occurs. Conversely, the use of the ionic [Rh(I)(COD)₂] BF₄ as the catalyst reveals an unexpected post-rearrangement that is characterized by the migration of the directing phosphino-group on the inserted aryl moiety. In this process, a concurrent cascade extension of the functionalization is also achieved by the introduction of a second aryl moiety. We focused our attention on the rhodium catalytic species formed, and the five or seven-membered rhodacycles as intermediates involved in these C–H catalytic cascade processes. Besides the electronic effects attached to Rh(I) and Rh(III) precatalysts, either cationic or neutral, our results clearly suggest the role of the pentamethylcyclopentadienyl substituent in the selectivity of peri-C–H-arylation. Conversely, rhodium stabilized by weakly bonded more fluxional bis-cyclooctadienyl ligands enters more easily into further reactivity, promoting 2-fold arylation reactions or even participate to diphenylphosphino group rearrangement.

## Introduction

Polycyclic aromatic hydrocarbons (PAHs) are π-extended aromatics that have found valuable applications in the field of coordination chemistry and catalysis,¹ as well as organic electronic materials (Figure 1, top).² These include planar aromatic pyrene, perylene, phenanthrene and fluoranthene derivatives, in which electronic and geometric features generally favour π-stacking.³ Their robustness and structural proximity with graphene and carbon nanotubes promote grafting and self-assembly.⁴

On the other hand, polyaryl derivatives are scaffolds recognized for their properties in valuable biomedical applications.⁵ The 2-biphenylyl moiety binds to a wide range of proteins with a high level of specificity, in addition to specific analgesic, anti-inflammatory, and antihypertensive bioactivity.⁶ Moreover, 2-biphenylyl-based phosphines have emerged as supporting ligands for catalytic transition metals, with various emblematic di- and monophosphine derivatives.⁷ The development of practical synthetic ways to access π-extended aromatic incorporating donor ligands is consequently very attractive, while only a few rhodium-catalyzed C–H activation/arylation methods directed by

<figure><img src="image_2.png" /><figcaption>State of art on the selective P-directed Rh-catalyzed arylation</figcaption></figure>

<figure><img src="image_3.png" /></figure>

**Figure 1.** π-Extended polyaromatic derivatives incorporating phosphino-, N-heterocarbene (NHC) or amino coordinating donor groups. State of art on the selected P-directed Rh-catalyzed arylation and this work: selective (poly)arylation on fluoranthenyl phosphine driven by Rh precursor.

a phosphine group have been reported to date (Figure 1, bottom).⁸⁻¹¹ While the selective monoarylation has been explored on 2-binaphthyl,⁹ᵃᵇ on indolyl,⁹ᶜ the P-directed rhodium-catalyzed polyarylation remains a challenging topic. Recently, Shi and You reported the selective (poly)arylation on 2-biphenylyl phosphines and directly on the triphenylphosphine.¹¹ Che and our group reported the selective monoarylation of more constrained polyaromatic phosphines such as naphthyl, pyrenyl, phenanthryl, or fluoranthenyl.⁹ᵈ,¹⁰ The C–H bond functionalization occurred through a five membered rhodacycle in the *peri*-position of the PAH in presence of Rh(I) or Rh(III) precatalyst. To the best of our knowledge, there is no example of the polyarylation on the polyaromatic phosphine such as fluoranthenyl, probably because it requires the formation of a less favoured seven-rhodacycle intermediate compared to previous polyarylation process.

In this work, we studied the precatalysts rhodium complexes and rhodacycles as possible intermediates involved in the cascade C–H catalytic processes. We demonstrated the role of
the highly hindering and electron-donating pentamethyl-
cyclopentadienyl substituent to obtain more selectively the single
peri-C–H-arylation using [RhCl₂Cp*]₂. Conversely, the less
hindered [Rh(COD)₂] BF₄ more readily engages in further
reactivity, including cascade arylation reactions, and even
participates to diphenylphosphino group rearrangement.

**Results and Discussion**

**Synthesis of peri-arylated fluoranthenyl diphenylphosphines.** Based on our previous works,¹⁰ the diphenylphosphino fluoranthene¹² **1** was selectively arylated in *peri*-position by P-directed C–H activation, using 5 mol% of the cationic [Rh(COD)₂] BF₄ with 1.5 equiv of a bromoarene, and K₃PO₄ in trifluorotoluene¹³ (0.165 M based on **1**). This synthetic route provides the π-extended aromatic phosphines **2a** to **10a** (Figure 2).

P-directed C–H arylation of **1** with 4-bromoanisole gave **2a** in 58% isolated yield with the diphenylphosphino moiety as the directing group. A full conversion was obtained with dialkylphosphines (*i*-Pr and Cy, **3** and **4** respectively), and **3a** and **4a** were isolated in 85% and 91% respectively. The protocol was successfully extended to the 3,5-dimethoxybromobenzene and the 3,4,5-trimethoxybromoben-zene to obtain the π-extended aromatic phosphine **5a** and **6a** in 96% and 73% isolated yield, respectively. The coupling of 1-bromopyrene, despite its intrinsic hindrance gave the π-extended aromatic phosphine **7a** in 80% isolated yield. The aryl bromides bearing cyano, chloro and acetyl electron-attracting groups were also tolerated but with a moderate selectivity to the monoarylation **Xa** (see infra and SI). The coupling reaction was further optimized to improve the selectivity in favour of **8a**, **9a** and **10a** by using the dimeric precatalyst [RhCl₂Cp*]₂.¹⁰b

<figure><img src="image_4.png" /></figure>

Conditions: fluoranthene monophosphane 1, 3-4 (0.5 mmol, 1 equiv), aryl bromide (1.5 equiv), K₃PO₄ (3.0 equiv), PhCF₃ (0.16 M) at reflux, 18 h under argon. Rh (I) = [Rh(COD)₂]BF₄ (5 mol%), ; Rh(III) = [RhCl₂Cp*]₂ (2.5 mol%) written in italics. Conversion based on the consumption of 1, 3-4. Isolated yields given in parentheses.

<caption>**Figure 2.** Synthesis of *peri*-arylated fluoranthenyl diphenylphosphines. H atoms and one CH₂Cl₂ are omitted for clarity (XRD of **8a**).</caption>

These protocols provided isolated yields of 51% for **8a**, and 50% and 69% for **9a** and **10a**, respectively. When comparing the Rh(I) cationic [Rh(COD)₂]BF₄ catalyst with the Rh(III) dimeric [RhCl₂(Cp*)]₂ one, Rh(I) gave a better conversion for all bromide derivatives. However, Rh(I) provided a lower selectivity for **Xa** due to its higher reactivity (vide infra and SI, Table S2 and S3), with aryl bromide bearing an electron-withdrawing group (CN, Cl and COMe). The dimeric [RhCl₂(Cp*)]₂ also provided slightly lower selectivity for aryl bromide bearing a donating group.

In order to examine the planarity of these polyaromatic
compounds, further analyses were conducted in the solid state.
Single crystals of **8a** suitable for solid state X-ray diffraction were
obtained under argon atmosphere (see molecular structure in
Figure 2 bottom, and crystal details in the Supporting
Information XRD). Interestingly, in the course of our
crystallization attempts, we observed the concomitant formation
of the phosphinate **8d**, fluoranthenyl-OP(O)Ph₂ (³¹P NMR in
CDCl₃, δ = 31.9 ppm), under air (XRD **8d** in SI, and Figure 3).
We easily formed the phosphine oxide **8e**, fluoranthenyl-
P(O)Ph₂ (³¹P NMR in CDCl₃, δ = 30.9 ppm), by oxidation with an
excess of hydrogen peroxide (10 equiv) for 4 h, however without
noting the puzzling suroxidation process observed under air in
longer time conditions that led to **8d**. Presumably, the
polyarylated phosphine reacts with singlet oxygen during the
crystallization process, by photooxidation (Scheme 1).¹⁴ The
insertion of the oxygen atom takes place on the electron-richer
aryl group to form the phosphinate ester (ie. on the arylated
fluoranthenyl moiety).
<figure><img src="image_5.png" /><figcaption>**Scheme 1.** Photosensitiser-free photooxidation process of polyarylated phosphines,¹⁴ to phosphinate ester **8d**.</figcaption></figure>

In their solid-state structure, the stacking of **8a** and **8d** (Figure 3) comes from intermolecular non-covalent interactions between i) the π-systems of the phenyl substituents of the phosphorus atoms, ii) the π-system of one fluoranthene and C–H bonds of

<figure><img src="image_6.png" /><figcaption>**Figure 3.** Packing of phosphinate **6d** in XRD with main noncovalent interaction that are present in the solid-state structure. Color codes: C in gray, P in purple, N in blue, O in red, H in white.</figcaption></figure>

another fluoranthene fragment, and iii) shallow H-bonds between the cyano groups and phenyl hydrogens. Additionally, π–π interactions are reinforced by some C–H–π interactions (details in SI).

Because of the seemingly facile oxidation of the fluoranthenyl phosphine **8a** in solution, we assessed the electron-donating character of the phosphorus in **1**, **3-4** and **2a-10a** from the measurement of their ¹J<sub>PSe</sub> spin-spin coupling constant (SSCC) after oxidative selenation and by comparison with SePPh<sub>3</sub> as benchmark (Table S-1 in SI).¹⁵,¹⁶ The 3-diphenylphosphino fluoranthene selenide **Se=1** (³¹P NMR in CDCl<sub>3</sub>, δ = 31.7 ppm) displayed a ¹J<sub>PSe</sub> = 722 Hz smaller than the benchmark used triphenylphosphine selenide (Se=PPh<sub>3</sub>) at 730 Hz. A decrease in these ¹J<sub>PSe</sub> coupling constants indicates a decrease in the s character of the phosphorus lone-pair orbital, i. e. an electron-donating effect of the phosphanyl group to the selenium atom. The electron-donor character of **1** is thus fairly comparable to PPh<sub>3</sub>, albeit slightly more basic. The aryl insertion on the peri-position of the diphenylphosphine group increase the ¹J<sub>PSe</sub> spin-spin coupling constant compared to the unsubstituted

phosphane (from 720 Hz to 750 Hz). This indicates a lower basicity of the phosphorus for the substituted monophosphine. On the contrary, the substituent (donating or attracting group) on the aryl insert has only a small influence, as the ¹J<sub>PSe</sub> spin-spin coupling constant barely change (around 750 Hz except for the pyrenyl moiety). A higher basicity is observed with the introduction of alkyl group directly on the phosphorus (**3a** (P-i-Pr<sub>2</sub>): 702 Hz and **4a** (PCy<sub>2</sub>): 694 Hz).

**Rhodacycles Activity in the P-directed Cascade Synthesis of π-Extended Aromatic Fluoranthenyl Phosphines.** We investigated the reasons for obtaining moderate yields for aryl-functionalized fluoranthenyl phosphines **8-10**. We found that this was notably due to the formation of numerous side-products, and that this was amplified by the use of the cationic complex [Rh(COD)<sub>2</sub>] BF<sub>4</sub> (Scheme 2).

<figure><img src="image_7.png" /><figcaption>**Scheme 2.** Rhodium complexes activity after C–H arylation of **1** with 4-bromobenzonitrile: cascade formation of **8b** and **8c** from C–H di- and tri-arylation, and **68f** from phosphino-group migration (average from duplicate experiments; ³¹P NMR recording in 202 MHz, in CDCl<sub>3</sub> are provided). Molecular structures of **8b**; thermal ellipsoids at 30% probabilities. H atoms are omitted for clarity (XRD **8b** and **8f**).</figcaption></figure>

For instance, the reaction of **1** with 4-bromobenzonitrile gave several products identified by NMR spectroscopy (see Scheme 1 and Table S-2 in the Supporting Information). Several reactions may take place after the initial C–H arylation by the action of [Rh(COD)<sub>2</sub>] BF<sub>4</sub>. Two or three consecutives C–H arylation processes occurred on compound **8a**, to successively yield **8b** and **8c**, respectively. The identification of **8c** was confirmed by the reaction of **8a** with two equiv of 4-bromobenzonitrile using [RhCl<sub>2</sub>Cp*]<sub>2</sub> (Table S-2 in the SI). Compound **8c** was isolated and characterized from a low 11%
conversion (see the 2D-NMR in SI, Figures S-41 to S-46). The processing of this cascade C–H functionalisation may logically involve the formation of a 7-membered rhodacycle intermediate, a type that has been rarely observed.¹⁷,¹⁸ We assume that the presence of the cyano electron-attracting substituent on the aryl substrate plays an activating role, as suggested by the analogous reactivity observed in the formation of **9a** and **10a**. Another puzzling side-product **8f** was formed in a significant 38% amount (Scheme 2, SI, Table S-2, entry 2). This might come from the rearrangement of **8a** with a migration of the phosphino-group after C–H arylation. The formation of **8b** (12% isolated yield, Table S-2, entry 6) was ascertained from single crystal X-ray diffraction analysis (Scheme 2 and SI XRD), showing that the first aryl inserted on **1** is almost perpendicular to the fluoranthenyl moiety with a dihedral angle equal to $\theta = 75.39(5)$, the second benzonitrile being directly linked to the first one on the *ortho*-position with a dihedral angle equal to $\theta' = 44.9(3)$. In the solid state, the packing of **8b** and **8f** comes from C–H–π interactions (as in **8a** and **8d**) but also from weak H-bonds between the cyano group and C–H bonds of the phosphorus phenyl substituents (Figure S7-10 in SI).

A thermal rearrangement process resulting in phosphino group migration and/or dephosphination (see below) is postulated (Scheme 3). The first Rh-catalyzed arylation gives the opportunity to form a 7-membered rhodacycle. These, are in general much less favored than 5 or 6-membered rhodacycles. Notably, herein this arrangement seems more accessible in the presence of the [Rh(COD)₂] BF₄ precatalyst. Rh insertion into the aryl–P bonds leads to the formation of a transient 6-membered Rh(III) phosphido–aryl species, which may subsequently undergo

<figure><img src="image_8.png" /><figcaption>**Scheme 3.** Dephosphination process and phosphino group migration. Reductive elimination to generate the dephosphination product or the phosphorus migration.¹⁹</figcaption></figure>

Since the use of a [Rh(III)Cl₂Cp*]₂ precatalyst favoured a cleaner single C–H arylation, we conversely attempted to optimize cascade C–H activation reactivity from the cationic

[Rh(II)(COD)₂] BF₄ (10 mol%) by using 3 equiv of the bromoarene (Scheme 4, see details in Table S-3 in the Supporting Information). Accordingly, the products **2b**, **9b** and **10b** were formed in a one-pot reaction in 35 to 50% yields, without the deleterious formation of migration product or further arylation reaction (Scheme 4). These results confirmed the influence of the substituent held by the aryl moiety on the consecutive C–H functionalization, since the best conversion arises with the presence of the electron-withdrawing acetyl substituent. Bis-arylated fluoranthenyl-phosphines could be formed with improved yields from the C–H arylation of arylated fluoranthenylphosphine **8a** and **10a**, leading to **8b** in 50% isolated yield, and **10b** in 43% yield. This stepwise approach also allows to diversify the R¹ and R² substituent groups on the aryl moiety, for instance R² as an acetyl substituent gave the π-extended aromatic fluoranthenyl phosphines **11b** in 25% isolated yield.

<figure><img src="image_9.png" /><figcaption>**Scheme 4.** (a) Cascade C–H diarylation of 1-diphenylphosphine fluoranthenes; (b) C–H arylation of compounds **8a** and **10a**. Conversion from ¹H NMR analysis with isolated yields in parentheses (averaged from duplicate experiments).</figcaption></figure>

**Identification of rhodium complexes and rhodacycles pertinent in the catalytic processes.** With the aim of better understanding the activity of rhodium complexes and the rhodacycles presumably involved in the various reactions that were identified (Scheme 1), we initially synthesized the complexes **12** and **13** (Scheme 5, top) by reacting **1** with the dimeric complex [Rh(III)Cl₂Cp*]₂. In a stoichiometric amount, in CH₂Cl₂ at room temperature, complex **12** was isolated in 92% isolated. By the addition of KOAc, the rhodacycle **13** resulting from a selective C–H activation at the C5-position of fluoranthene was formed in quantitative yield. Complex **12** featured a resonance in ³¹P NMR at 30.5 ppm (d, ¹JₚRh = 145 Hz, in CDCl₃), while the *peri*-metalation in rhodacycle **13** is characterized by a resonance at 65.0 ppm with a ¹JₚRh = 163 Hz. The complexes **12** and **13** were tested as catalyst (5 mol%) in the P-directed arylation reaction using 1-diphenylphosphine fluoranthene **1** and 4-bromobenzonitrile (1.5 equiv) under the general conditions (see SI, Table S2, entries 9 and 10).¹⁰b They demonstrated a higher reactivity than using the [RhCl₂Cp*]₂ precatalyst but a lower selectivity than both Rh(I) and Rh(III).
precatalyst with 31% and 43% conversion for **8a** for complex **12** and **13** respectively. The synthesis of a 7-membered rhodacycle was further attempted under the similar conditions (Scheme 5, bottom). In dichloroethane at 80 °C, a small amount of the complex **14** is formed, presumably featuring a linear coordination of the rhodium

<figure><img src="image_10.png" /></figure>

**Scheme 5.** Complexes **12** and **13** identified in solution from 3-diphenylphosphine fluoranthene **1** reactivity with rhodium complexes and proposed rhodium structures from **8a** reactivity. Solid state molecular structures of complex **12** (XRD **12**) and **13** (XRD **13**) formed from 3-diphenylphosphine fluoranthene **1** (thermal ellipsoids at 30% probabilities, H atoms and two CH₂Cl₂ for **13** are omitted for clarity).

to ligand **8a** as suggested by ¹H NMR (see Figure S1 in the Supporting Information) and ³¹P NMR (δ resonance at 35.8 ppm, ¹J<sub>PRh</sub> = 142 Hz) together with the rhodacycle **15** suggested by a resonance at 65.8 ppm ( ¹J<sub>PRh</sub> = 164 Hz).

A complex mixture of additional minor side-products was also detected, some identified as the product of dephosphination of **8g** (interestingly probing the possibility of removing the directing group), and other being precursor derivatives of phosphonate **8d** and phosphine oxide **8e**. The structural analysis of complexes **12** and **13** from the isolation of single crystals suitable for XRD (Scheme 5 and SI_XRD), confirmed for **12** the P-monocoordination of the ligand with a bond *d* P–Rh = 2.3527(13) Å. The pentamethylcyclopentadienyl ligand (Cp*) ligand lies almost parallel to the fluoranthenyl (Scheme 5, XRD of **12**). Analyses of the non covalent interactions in the crystal also revealed many C–H–π interactions between the methyl groups of the Cp* ligand and the fluoranthenyl and a phenyl substituent of the phosphorus atom (Figure S-Th 13 in SI). The X-ray analysis of **13** confirmed the rhodacycle formation from the *peri*-position (C5) of the fluoranthenyl, and a bond *d* P–Rh = 2.2897(10) Å, and *d* C11–Rh = 2.053(4) Å, for an angle P–Rh–C11 of 82.43(11) ° (Scheme 5, XRD of **13**). The geometry of the rhodium complex is tetrahedral with the pentamethylcyclopentadienyl (Cp*) almost perpendicular to the fluoranthenyl moiety (angles between the Cp* and the

fluoranthenyl plane: 76.99(4); Cp* centroid–Rh–C11: 130.79(13) ° and Cp* centroid–Rh–P: 132.21(5) °).

The somewhat lower yields obtained for the cascade reactions might be explained by the difficulty to form the 7-membered rhodacycles, which should be the key intermediate of such transformations. This process is also in competition with the formation of other concurrent resting states as suggested by the X-ray structure of complex **16** (Figure 4, top). Complex **16** was isolated during the one-pot synthesis of **10b** (Scheme 2, **a**)), and is obtained after three C–H bond activation involving two equiv. of **1** and 4-bromo-acetophenone. On the ³¹P NMR spectra of **16**, two signals as dd at 41.5 ppm ( ¹J<sub>PRh</sub> = 85 Hz and ²J<sub>PP</sub>* = 20 Hz, Figure 4 bottom) and 40.2 ppm ( ¹J<sub>PRh</sub> = 85 Hz and ²J<sub>PP</sub>* = 20 Hz) can be observed. The noncovalent interaction analyses of the solid-state structure of complex **16** revealed a stabilizing weak attractive interaction between the lone-pair of the Br atom and the π-electrons of the neighbouring phenyl substituent of the phosphorus atom (Figure S-Th 19 in SI). This interaction echoes the previously seen intermolecular C–H–π and π–π interactions.

Besides the electronic effects attached to Rh(I) and Rh(III) precatalysts, either cationic or neutral, the crystal structures of **12**, **13** and **16** clearly suggest the role of the highly hindering and electron-donating pentamethylcyclopentadienyl substituent in the selectivity of *peri*-C–H–arylation. The attachment of Cp* to Rh during the catalytic cycle precludes further reaction. Conversely, much less hindered rhodium centers, stabilized by weakly bonded more fluxional bis-cyclooctadienyl ligands, may more easily enter into further reactivity, including cascade arylation reactions or even participate to diphenylphosphino group rearrangement. This provides pertinent clues for the functionalization of congested polyaromatic substrates and the easier access to highly functionalized π-extended aromatics.

<figure><img src="image_11.png" /></figure>
**Figure 4.** Molecular structure of 16; thermal ellipsoids at 30% probabilities. H atoms and two CH₂Cl₂ are omitted for clarity (molecular structure of 16). ³¹P NMR spectra (CDCl₃, 202 MHz) of the Rh(III) metallacycle 16.

Based on our results and previous studies,⁹⁻¹¹ we propose a mechanism of the rhodium-catalyzed P-directed arylation on the fluoroanthenyl phosphine in Scheme 6. Starting from the cationic [Rh(COD)₂]BF₄, a ligand exchange of the two bis(cyclooctadienyl) ligands with two fluoroanthene monophosphane (L: 1, R = Ph; 3, R = t-Pr, 4, R = Cy) led to the formation of the complex 17. The *ortho*-metalation occurred from complex 17 by an intramolecular concerted metallation-deprotonation assisted by the base to form the 5-membered rhodacycle 18. Oxidative addition of aryl bromide to complex 18 led to complex 19. Complex 20 is formed by reductive elimination and formation of the C–C bond on the *peri*-position of L. The arylated product is released and replaced by a non-arylated phosphine ligand, regenerating 17. The monoarylated fluoroanthenyl phosphine can enter into an alternative catalytic cycle through a 7-membered rhodacycle (Scheme 3), which is favoured with [Rh(COD)₂]BF₄ precatalysts compared to the bulkier dimeric [RhCl₂Cp*]₂.

<figure><img src="image_12.png" /><figcaption>**Scheme 6.** Mechanistic proposal for diphenyl-1-fluoroanthenyl phosphines P-arylation.</figcaption></figure>

## Conclusion

We reported the synthesis by P-directed C–H arylation of a new class of polyarylated diphenyl-1-fluoroanthenyl phosphines. The [Rh(III)Cl₂Cp*]₂ complex selectively favored a single *peri*-functionalization of the polycyclic aromatic hydrocarbon phosphine. Conversely, the cationic [Rh(II)(COD)₂]BF₄ precatalyst allowed a cascade process leading to the extension of the functionalization by the introduction of a second aryl moiety which tolerated electron-donating or withdrawing substituents through a 7-membered rhodacycle. This key intermediate also permitted the migration of the phosphino-group on the newly inserted aryl.

## Experimental Section

**Accession Codes.** CCDC 2245456 (8a), 2245459 (8b), 2245453 (8d), 2245457 (8f), 2245455 (12), 2245454 (13), 2245458 (E16) contain the supplementary crystallographic data for the paper. These data can be obtained free of charge via

www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

**Materials and Methods.** All reagents were purchased from commercial suppliers and used without purifications. All reactions were performed in Schlenk tubes equipped with a magnetic stirring bar. ¹H (500 MHz), ¹³C (125 MHz), ³¹P (202 MHz) spectra were recorded on Brucker AVANCE NEO instrument. Chemical shifts are reported in ppm relative to CDCl₃ (¹H: 7.26 and ¹³C: 77.16) and coupling constants *J* are given in Hz. High resolution mass spectra (HRMS) were recorded on a Orbitrap Exploris 240 mass spectrometer (thermo Scientific) equipped with an electrospray ionization source (HESI). Elemental analysis experiments were recorded on a Thermo Electron Flash EA 1112 Series.

**Synthesis of the 5-(poly)arylated 3-fluoroanthenylphosphine ligands (2x-11x)** A Schlenk tube was charged with 1-fluoroanthene phosphine (1 equiv, 0.5 mmol, 192 mg), aryl bromide (1.5-3.0 equiv), K₃PO₄ (3 equiv, 1.5 mmol, 318 mg), and [Rh(COD)₂]BF₄ or [RhCl₂Cp*]₂ (5-10 mol%, [Rh]: 10 mol%), in dry PhCF₃ (0.165 M, 3 ml) and heat at reflux during 18 h under argon. After extraction, the organic layer was concentrated in vacuum and was purified by column chromatography using as eluent a mixture pentane or heptane/dichloromethane.

**[5-(4-methoxyphenyl)-3-fluoroanthenyl]diphenyl phosphine (2a)** ¹H NMR (500 MHz, CDCl₃), δ: 7.92 (t, *J* = 7.2 Hz, 2H), 7.87 (d, *J* = 6.8 Hz, 1H), 7.80 (d, *J* = 7.2 Hz, 1H), 7.41–7.35 (m, 3H), 7.28–7.20 (m, 7H), 7.03 (m, 6H), 6.67 (d, *J* = 8.6 Hz, 2H), 3.84 (s, 3H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –8.5 (s) ppm.

**[5-(4-methoxy-2-(4-methoxyphenyl)-phenyl)-3-fluoroanthenyl]diphenyl phosphine (2b)** ¹H NMR (500 MHz, CDCl₃), δ: 7.86 (t, *J* = 6.1 Hz, 2H), 7.82 (d, *J* = 7.1 Hz, 1H), 7.76 (d, *J* = 7.2 Hz, 1H), 7.38 (p, *J* = 8.0 and 7.3 Hz, 3H), 7.34–7.21 (m, 11H), 7.03 (t, *J* = 7.1 Hz, 5H), 6.64 (d, *J* = 8.7 Hz, 2H), 6.61 (d, *J* = 8.4 Hz, 1H), 6.34 (dd, *J* = 8.4 and 2.6 Hz, 1H), 3.88 (s, 3H), 3.68 (s, 3H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –10.2 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 159.8, 158.3, 142.3 (d, *J*<sub>PC</sub> = 5.7 Hz), 141.2 (d, *J*<sub>PC</sub> = 2.8 Hz), 140.4, 140.2, 139.6, 139.1, 138.4, 138.0 (d, *J*<sub>PC</sub> = 13.8 Hz), 137.9, 136.6 (d, *J*<sub>PC</sub> = 1.8 Hz), 136.2, 136.0, 134.4, 134.3 (d, *J*<sub>PC</sub> = 20.5 Hz), 134.0 (d, *J*<sub>PC</sub> = 20.5 Hz), 133.6 (d, *J*<sub>PC</sub> = 16.5 Hz), 133.4 (d, *J*<sub>PC</sub> = 8.1 Hz), 133.3, 133.1 (d, *J*<sub>PC</sub> = 4.0 Hz), 133.0, 131.0 (d, *J*<sub>PC</sub> = 2.8 Hz), 128.6 (d, *J*<sub>PC</sub> = 3.2 Hz), 128.5, 128.2 (d, *J*<sub>PC</sub> = 9.0 Hz), 128.1 (d, *J*<sub>PC</sub> = 9.0 Hz), 127.6, 121.7, 121.3, 120.0, 119.8, 115.6, 113.2, 111.7, 55.6, 55.2 ppm. Elemental analysis (%) calcd for C₄₂H₃₁O₂P: C, 84.26; H, 5.22; Found: C, 81.41; H, 4.35. HRMS+pESI (m/z) [M+H]⁺ Calcd.: 599.21344, Found: 599.213570.

**[5-(4-methoxyphenyl)-3-fluoroanthenyl]di-isopropyl phosphine (3a)** ¹H NMR (500 MHz, CDCl₃), δ: 7.87 (d, *J* = 7.2 Hz, 1H), 7.83 (t, *J* = 6.6 Hz, 3H), 7.78 (d, *J* = 7.3 Hz, 1H), 7.39 (d, *J* = 7.0 Hz, 1H), 7.34–7.28 (m, 2H), 7.17 (d, *J* = 9.5 Hz, 3H), 6.88 (d, *J* = 8.7 Hz, 2H), 3.83 (s, 3H), 1.85 (p, *J* = 7.0 Hz, 2H), 0.79 (dd, *J* = 13.8, 6.9 Hz, 6H), 0.72 (dd, *J* = 12.1, 7.0 Hz, 6H). ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –2.9 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 159.3, 142.3, 139.3, 139.1, 138.1 (d, *J*<sub>PC</sub> = 37.7 Hz), 137.7, 136.7, 136.6 (d, *J*<sub>PC</sub> = 1.1 Hz), 134.6, 134.4 (d, *J*<sub>PC</sub> = 1.0 Hz), 133.4 (d, *J*<sub>PC</sub> = 6.5 Hz), 132.2 (d, *J*<sub>PC</sub> = 6.9 Hz), 132.0, 127.9, 127.5, 121.5, 121.2, 119.4 (d, *J*<sub>PC</sub> = 29.2 Hz), 113.3, 55.6,
25.9 (d, $J_{PC}$ = 20.2 Hz), 20.3 (d, $J_{PC}$ = 14.1 Hz), 20.0 (d, $J_{PC}$ = 20.2 Hz). ppm. Elemental analysis (%) calcd for C₂₅H₂₉OP: C, 82.05; H, 6.89; Found: C, 83.12; H, 7.05. HRMS+pESI (m/z) [M+H]⁺ Calcd.: 425.20288, Found: 425.20237.

**[5-(4-methoxyphenyl)-3-fluoranthenyl]dicyclohexyl phosphine (4a)**
¹H NMR (500 MHz, CDCl₃), δ: 7.99–7.86 (m, 5H), 7.47 (dd, *J* = 6.9, 2.1 Hz, 1H), 7.43–7.37 (m, 2H), 7.24 (d, *J* = 4.6 Hz, 2H), 7.00–6.94 (m, 2H), 3.92 (s, 3H), 1.79–1.71 (m, 2H), 1.66 (d, *J* = 12.1 Hz, 4H), 1.57 (d, *J* = 10.7 Hz, 4H), 1.47 (d, *J* = 14.0 Hz, 2H), 1.30–1.01 (m, 7H), 0.97–0.84 (m, 4H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –12.4 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 159.2, 142.3 (d, $J_{PC}$ = 0.8 Hz), 139.3 (d, $J_{PC}$ = 17.5 Hz), 137.6, 137.3, 137.0, 136.8 (d, $J_{PC}$ = 5.0 Hz), 136.7 (d, $J_{PC}$ = 0.8 Hz), 134.8, 134.8, 134.7, 133.4 (d, $J_{PC}$ = 5.5 Hz), 132.1 (1d, $J_{PC}$ = 6.9 Hz), 132.0, 127.8, 127.4, 121.4 (d, $J_{PC}$ = 23.4 Hz), 119.4 (d, $J_{PC}$ = 27.1 Hz), 113.2, 55.6, 36.3 (d, $J_{PC}$ = 20.8 Hz), 30.3 (d, $J_{PC}$ = 8.7 Hz), 29.9 (d, $J_{PC}$ = 11.5 Hz), 27.4 (d, $J_{PC}$ = 8.3 Hz), 27.3 (d, $J_{PC}$ = 11.5 Hz), 26.6 ppm. Elemental analysis (%) calcd for C₃₅H₃₇OP: C, 83.30; H, 7.39; Found: C, 84.11; H, 7.51. HRMS+pESI (m/z) [M+H]⁺ Calcd.: 505.26548, Found: 505.26495.

**[5-(3,5-dimethoxyphenyl)-3-fluoranthenyl]diphenyl phosphine (5a)**
¹H NMR (500 MHz, CDCl₃), δ: 7.94 (d, *J* = 7.1 Hz, 1H), 7.92 (d, *J* = 7.1 Hz, 1H), 7.88 (d, *J* = 7.3 Hz, 1H), 7.82 (d, *J* = 7.2 Hz, 1H), 7.47 (d, *J* = 7.0 Hz, 1H), 7.42 (m, 2H), 7.31 (dd, *J* = 7.2 and 4.1 Hz, 1H), 7.25–7.21 (m, 6H), 7.04 (t, *J* = 6.9 Hz, 4H), 6.46 (t, *J* = 2.2 Hz, 1H), 6.28 (sb, 2H), 3.52 (s, 6H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –10.4 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 160.0, 144.3, 144.3, 141.9 (d, $J_{PC}$ = 2.1 Hz), 139.5 (d, $J_{PC}$ = 16.8 Hz), 139.3, 138.9, 138.3, 138.3, 137.2 (d, $J_{PC}$ = 1.9 Hz), 136.7 (d, $J_{PC}$ = 31.3 Hz), 133.8 (d, $J_{PC}$ = 20.9 Hz), 133.3 (d, $J_{PC}$ = 5.5 Hz), 132.4 (d, $J_{PC}$ = 21.5 Hz), 131.3, 128.4 (d, $J_{PC}$ = 6.4 Hz), 128.2, 128.1, 127.7, 121.6, 121.3, 119.9, 119.6, 109.1 (d, $J_{PC}$ = 6.6 Hz), 100.6, 55.1 ppm. Elemental analysis (%) calcd for C₃₆H₂₇O₂P: C, 82.74; H, 5.21; Found: C, 82.82; H, 5.28. HRMS+pESI (m/z) [M+Na]⁺ Calcd.: 545.16409, Found: 545.16158.

**[5-(3,4,5-trimethoxyphenyl)-3-fluoranthenyl]diphenyl phosphine (6a)**
¹H NMR (500 MHz, CDCl₃), δ: 7.94 (d, *J* = 7.1 Hz, 1H), 7.89 (dd, *J* = 21.2 and 7.1 Hz, 2H), 7.81 (d, *J* = 7.2 Hz, 1H), 7.47 (d, *J* = 7.1 Hz, 1H), 7.43–7.36 (m, 2H), 7.28–7.25 (m, 3H), 7.22 (t, *J* = 7.3 Hz, 4H), 7.01 (t, *J* = 7.0 Hz, 4H), 6.32 (d, *J* = 1.4 Hz, 2H), 3.94 (s, 3H), 3.53 (s, 6H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –9.6 (s) ppm.

**[5-(1-pyrenyl)-3-fluoranthenyl]diphenyl phosphine (7a)**
¹H NMR (500 MHz, CDCl₃), δ: 8.22 (d, *J* = 7.4 Hz, 1H), 8.17–8.12 (m, 2H), 8.08–8.04 (m, 2H), 8.04–7.97 (m, 3H), 7.94 (d, *J* = 6.9 Hz, 1H), 7.88 (d, *J* = 7.1 Hz, 1H), 7.80 (d, *J* = 7.7 Hz, 1H), 7.63 (m, 2H), 7.50–7.40 (m, 3H), 7.30–7.24 (m, 2H), 7.19 (t, *J* = 7.2 Hz, 2H), 6.90 (t, *J* = 7.3 Hz, 1H), 6.78 (t, *J* = 7.1 Hz, 2H), 6.72 (t, *J* = 7.3 Hz, 2H), 6.45 (t, *J* = 7.3 Hz, 2H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –11.0 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 140.4 (d, $J_{PC}$ = 2.7 Hz), 139.5, 139.1, 139.1 (d, $J_{PC}$ = 16.1 Hz), 138.7, 137.9, 137.7, 137.6 (d, $J_{PC}$ = 6.2 Hz), 137.6, 137.1, 136.8, 133.8 (d, $J_{PC}$ = 20.5 Hz), 133.6 (d, $J_{PC}$ = 21.6 Hz), 133.5, 133.4 (d, $J_{PC}$ = 2.1 Hz), 133.0, 131.6, 131.4 (d, $J_{PC}$ = 6.2 Hz), 131.3 (d, $J_{PC}$ = 0.7 Hz), 129.7 (d, $J_{PC}$ = 6.5 Hz), 128.3 (d, $J_{PC}$ = 7.7 Hz), 128.2 (d, $J_{PC}$ = 2.0 Hz), 128.0, 127.9, 127.9 (d, $J_{PC}$ = 2.9 Hz), 127.8, 127.5, 127.1, 126.0, 125.9, 125.1 (d, $J_{PC}$ = 3.2 Hz), 125.0, 124.8, 124.2, 121.8 (d; $J_{PC}$ = 26.4 Hz), 120.2 (d, $J_{PC}$ = 36.1 Hz) ppm. Elemental analysis (%) calcd for C₄₅H₂₇P: C, 90.08; H,

4.64; Found: C, 89.91; H, 4.60. HRMS+pESI (m/z) [M+Na]⁺ Calcd.: 609.17426, Found: 609.17520.

**[5-(4-cyanophenyl)-3-fluoranthenyl]diphenyl phosphine (8a)**
¹H NMR (500 MHz, CDCl₃), δ: 7.80 (t, *J* = 7.1 Hz, 2H), 7.75 (d, *J* = 6.8 Hz, 1H), 7.69 (d, *J* = 7.2 Hz, 1H), 7.29 (m, 4H), 7.19 (t, *J* = 6.5 Hz, 3H), 7.13 (t, *J* = 6.9 Hz, 5H), 7.08 (d, *J* = 7.6 Hz, 2H), 6.88 (t, *J* = 7.3 Hz, 4H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –8.7 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 147.4 (d, $J_{PC}$ = 3.7 Hz), 139.8 (d, $J_{PC}$ = 1.9 Hz), 139.0 (d, $J_{PC}$ = 6.0 Hz), 138.6, 138.2 (d, $J_{PC}$ = 1.7 Hz), 138.0, 137.9, 137.7, 135.9 (d, $J_{PC}$ = 28.9 Hz), 134.1 (d, $J_{PC}$ = 20.6 Hz), 133.4 (d, $J_{PC}$ = 5.4 Hz), 131.8, 131.7, 131.7, 131.6 (d, $J_{PC}$ = 21.0 Hz), 131.1, 128.8, 128.5 (d, $J_{PC}$ = 6.9 Hz), 128.3, 128.1, 121.7 (d, $J_{PC}$ = 20.6 Hz), 120.2, 119.5, 119.4, 110.8 ppm. Elemental analysis (%) calcd for C₃₅H₂₂NP: C, 86.23; H, 4.55; Found: C, 86.17; H, 4.53. HRMS+pESI (m/z) [M+Na]⁺ Calcd.: 510.13821, Found: 510.13953.

**[5-(4-cyano-2-(4-cyanophenyl)-phenyl)-3-fluoranthenyl]diphenyl phosphine (8b)**
¹H NMR (500 MHz, CDCl₃), δ: 7.75–7.67 (m, 3H), 7.63 (d, *J* = 7.2 Hz, 1H), 7.58 (s, 1H), 7.26 (s, 5H), 7.20 (m, 2H), 7.14 (m, 5H), 7.09–7.03 (m, 2H), 7.01 (d, *J* = 7.8 Hz, 1H), 6.85 (t, *J* = 6.9 Hz, 2H), 6.78 (t, *J* = 7.6 Hz, 2H), 6.72 (d, *J* = 7.8 Hz, 1H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –10.1 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 145.6 (d, $J_{PC}$ = 3.5 Hz), 144.3, 140.8 (d, $J_{PC}$ = 5.5 Hz), 138.9, 138.8, 138.2 (d, $J_{PC}$ = 1.8 Hz), 138.1, 138.1 (d, $J_{PC}$ = 14.7 Hz), 137.6 (d, $J_{PC}$ = 3.2 Hz), 136.6 (d, $J_{PC}$ = 3.2 Hz), 134.7, 134.5, 133.9 (d, $J_{PC}$ = 20.3 Hz), 133.8 (d, $J_{PC}$ = 20.0 Hz), 133.3 (d, $J_{PC}$ = 6.0 Hz), 133.0 (d, $J_{PC}$ = 4.3 Hz), 132.9, 132.3, 132.1 (d, $J_{PC}$ = 22.3 Hz), 131.7, 130.8, 130.3 (d, $J_{PC}$ = 3.2 Hz), 129.0, 128.8, 128.8 (d, $J_{PC}$ = 6.3 Hz), 128.5 (d, $J_{PC}$ = 7.1 Hz), 128.5, 128.2, 121.8 (d, $J_{PC}$ = 26.9 Hz), 120.5, 119.4, 118.8 (d, $J_{PC}$ = 22.6 Hz), 112.1, 111.2 ppm. Elemental analysis (%) calcd for C₄₂H₂₅N₂P: C, 85.70; H, 4.28; Found: C, 85.34; H, 4.15. HRMS+pESI (m/z) [M+H]⁺ Calcd.: 587.16716, Found: 587.16793.

**[5-(4-cyano-2,6-bis(4-cyanophenyl)-phenyl)-3-fluoranthenyl]diphenyl phosphine (8c)**
¹H NMR (500 MHz, CDCl₃), δ: 7.72 (dt, *J* = 8.4 and 4.6 Hz, 2H), 7.64 (d, *J* = 3.9 Hz, 2H), 7.57 (d, *J* = 7.2 Hz, 1H), 7.28 (td, *J* = 7.6, 7.1 and 4.1 Hz, 4H), 7.18 (m, 7H), 7.09 (d, *J* = 8.2 Hz, 4H), 6.98 (d, *J* = 7.1 Hz, 1H), 6.83 (t, *J* = 7.0 Hz, 4H), 6.74 (d, *J* = 8.2 Hz, 4H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –12.8 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 143.9 (d, $J_{PC}$ = 3.4 Hz), 143.8, 142.8 (d, $J_{PC}$ = 4.4 Hz), 139.3, 138.8, 138.6 (d, $J_{PC}$ = 1.9 Hz), 138.3, 136.8 (d, $J_{PC}$ = 4.3 Hz), 136.7 (d, $J_{PC}$ = 3.4 Hz), 134.2 (d, $J_{PC}$ = 13.7 Hz), 134.6 (d, $J_{PC}$ = 11.9 Hz), 134.2, 134.0, 133.8, 133.5 (d, $J_{PC}$ = 6.5 Hz), 133.2, 132.4 (d, $J_{PC}$ = 23.0 Hz), 131.4, 130.4, 129.2, 128.9 (d, $J_{PC}$ = 6.5 Hz), 128.6 (d, $J_{PC}$ = 17.5 Hz), 121.9, 121.7, 120.3, 118.9, 118.5, 118.4, 113.1, 111.1 ppm. Elemental analysis (%) calcd for C₄₉H₂₈N₃P: C, 85.33; H, 4.09; Found: C, 85.34; H, 4.15. HRMS+pESI (m/z) [M-H]⁺ Calcd.: 688.19359, Found: 688.19371.

**[5-(4-chlorophenyl)-3-fluoranthenyl]diphenyl phosphine (9a)**
¹H NMR (500 MHz, CDCl₃), δ: 7.73 (t, *J* = 6.4 Hz, 2H), 7.69 (d, *J* = 6.5 Hz, 1H), 7.63 (d, *J* = 7.3 Hz, 1H), 7.56 (d, *J* = 8.2 Hz, 2H), 7.25–7.18 (m, 3H), 7.16–7.11 (m, 3H), 7.09–7.03 (m, 5H), 6.89–6.82 (m, 3H) ppm.
³¹P{¹H} NMR (202 MHz, CDCl₃), δ: –9.2 ppm.
¹³C NMR (125 MHz, CDCl₃), δ: 198.1, 147.5, 140.8, 139.1 (d, $J_{PC}$ = 23.0 Hz), 138.4, 138.3, 137.8, 137.7 (d, $J_{PC}$ = 1.7 Hz), 136.2 (d, $J_{PC}$ = 29.5 Hz), 134.1 (d, $J_{PC}$ = 20.6 Hz), 133.4 (d, $J_{PC}$ = 5.5 Hz), 131.9 (d, $J_{PC}$ = 1.2 Hz), 131.7, 131.2 (d, $J_{PC}$ = 6.1 Hz), 130.0, 128.6, 128.4 (d, $J_{PC}$ = 12.2 Hz), 128.2 (d, $J_{PC}$ = 44.6 Hz),
127.5, 121.6 (d, $J_{PC}$ = 24.3 Hz), 120.1, 119.5 ppm. Elemental analysis (%) calcd for C₃₄H₂₂ClP: C, 82.17; H, 4.46; Found: C, 80.66; H, 4.12. HRMS+pESI (m/z) [2M+H]⁺ Calcd.: 497.12259, Found: 497.12140.

[5-(4-chloro-2-(4-chlorophenyl)phenyl)-3-fluorананthenyl]diphenyl phosphine (9b) ¹H NMR (500 MHz, CDCl₃), δ: 7.87 (t, $J = 7.2$ Hz, 2H), 7.83 (d, $J = 7.1$ Hz, 1H), 7.78 (d, $J = 7.2$ Hz, 1H), 7.45 (d, $J = 2.1$ Hz, 1H), 7.44–7.32 (m, 4H), 7.32–7.22 (m, 9H), 7.09 (d, $J = 8.5$ Hz, 2H), 7.05–6.98 (m, 3H), 6.81 (dd, $J = 8.1$, 2.1 Hz, 1H), 6.65 (d, $J = 8.1$ Hz, 1H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: -10.3 ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 139.4 (d, $J_{PC} = 5.5$ Hz), 139.3, 139.21 (d, $J_{PC} = 2.9$ Hz), 139.1, 139.0, 139.0 (d, $J_{PC} = 4.0$ Hz), 138.9, 138.6, 138.0, 137.3 (d, $J_{PC} = 1.8$ Hz), 137.2 (d, $J_{PC} = 12.3$ Hz), 135.5 (d, $J_{PC} = 28.7$ Hz), 134.1 (d, $J_{PC} = 16.4$ Hz), 134.0, 133.9 (d, $J_{PC} = 16.5$ Hz), 133.4 (d, $J_{PC} = 4.3$ Hz), 133.3 (d, $J_{PC} = 6.0$ Hz), 133.0, 132.8 (d, $J_{PC} = 31.8$ Hz), 132.6, 131.0 (d, $J_{PC} = 3.0$ Hz), 129.6, 128.7 (d, $J_{PC} = 17.4$ Hz), 128.6 (d, $J_{PC} = 22.9$ Hz), 128.3, 128.2, 128.0, 127.8, 127.7 (d, $J_{PC} = 12.2$ Hz), 126.8, 121.7 (d, $J_{PC} = 32.9$ Hz), 120.1, 119.5. Elemental analysis (%) calcd for C₃₅H₂₅Cl₂P: C, 79.08; H, 4.15; Found: C, 74.04; H, 4.12. HRMS+pESI (m/z) [M+H]⁺ HRMS+pESI (m/z) [M+H]⁺ Calcd.: 607.11492, Found: 607.11378.

[5-(4-acetylphenyl)-3-fluorананthenyl]diphenyl phosphine (10a) ¹⁰b ¹H NMR (500 MHz, CDCl₃), δ: 7.98–7.91 (m, 2H), 7.89 (dd, $J = 6.3$, 1.3 Hz, 1H), 7.83 (d, $J = 7.2$ Hz, 1H), 7.73 (d, $J = 8.2$ Hz, 2H), 7.43 (qd, $J = 7.0$, 6.6, 1.2 Hz, 2H), 7.38 (d, $J = 7.1$ Hz, 1H), 7.34–7.27 (m, 4H), 7.27–7.20 (m, 6H), 7.01 (t, $J = 7.8$ Hz, 4H), 2.66 (s, 3H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: -9.2 (s) ppm.

[5-(4-acetylphenyl)-3-fluorананthenyl]diphenyl phosphine (10b) ¹H NMR (500 MHz, CDCl₃), δ: 8.17 (d, $J = 1.8$ Hz, 1H), 7.91–7.85 (m, 2H), 7.85–7.78 (m, 4H), 7.59–7.54 (m, 2H), 7.46 (dd, $J = 7.8$ and 1.9 Hz, 1H), 7.41 (qd, $J = 6.9$, 6.2 and 1.4 Hz, 3H), 7.33 (qd, $J = 5.5$, 4.8 and 1.5 Hz, 6H), 7.29 (d, $J = 7.1$ Hz, 1H), 7.10 (td, $J = 7.4$, 6.1 and 3.5 Hz, 2H), 7.05 (td, $J = 7.9$ and 1.3 Hz, 2H), 6.92 (d, $J = 7.9$ Hz, 1H), 2.72 (s, 3H), 2.51 (s, 3H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: -11.0 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 198.1, 198.0, 146.0, 145.9 (d, $J_{PC} = 3.7$ Hz), 140.7 (d, $J_{PC} = 5.2$ Hz), 139.3 (d, $J_{PC} = 17.1$ Hz), 139.2, 138.8, 138.5, 137.7 (d, $J_{PC} = 1.7$ Hz), 137.2 (d, $J_{PC} = 1.8$ Hz), 136.8, 135.5, 134.1 (d, $J_{PC} = 20.0$ Hz), 134.0 (d, $J_{PC} = 20.0$ Hz), 133.4 (d, $J_{PC} = 6.2$ Hz), 132.9, 132.8 (d, $J_{PC} = 18.3$ Hz), 132.4, 130.1 (d, $J_{PC} = 3.0$ Hz), 129.7, 129.2, 128.9 (d, $J_{PC} = 23.5$ Hz), 128.8 (d, $J_{PC} = 18.3$ Hz), 128.5, 128.4 (d, $J_{PC} = 7.4$ Hz), 128.1, 128.0, 127.7, 127.2, 121.8, 121.6, 120.4, 119.6, 27.0, 26.8 ppm. Elemental analysis (%) calcd for C₄₄H₃₁O₂P: C, 84.87; H, 5.02; Found: C, 79.36; H, 4.01. HRMS+pESI (m/z) [M+H]⁺ Calcd.: 623.21344, Found: 623.21381.

[5-(4-cyano-2-(4-acetylphenyl)-phenyl)-3-fluorананthenyl]diphenyl phosphine (11b) ¹H NMR (500 MHz, CDCl₃), δ: 7.88–7.81 (m, 2H), 7.79 (d, $J = 7.1$ Hz, 1H), 7.78–7.72 (m, 2H), 7.70 (d, $J = 8.4$ Hz, 2H), 7.45–7.36 (m, 4H), 7.36–7.31 (m, 1H), 7.27 (q, $J = 7.0$ Hz, 5H), 7.19 (dd, $J = 7.1$, 3.2 Hz, 2H), 7.08 (dd, $J = 7.8$, 1.7 Hz, 1H), 7.02–6.97 (m, 2H), 6.93 (t, $J = 7.3$ Hz, 2H), 6.81 (d, $J = 7.9$ Hz, 1H), 2.47 (s, 3H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: -10.6 ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 197.8, 145.7 (d, $J_{PC} = 3.5$ Hz), 144.5, 141.5 (d, $J_{PC} = 5.5$ Hz), 139.1 (d, $J_{PC} = 13.6$ Hz), 138.8, 138.5 (d, $J_{PC} = 15.3$ Hz), 138.4, 138.2 (d, $J_{PC} = 3.3$ Hz), 138.0 (d, $J_{PC} = 1.9$ Hz), 136.8 (d, $J = 11.1$ Hz), 135.8, 135.0 (d, $J = 27.4$ Hz), 133.9 (d, $J_{PC} = 4.5$ Hz),

133.8 (d, $J_{PC} = 4.1$ Hz), 133.3 (d, $J_{PC} = 6.0$ Hz), 133.1, 133.0 (d, $J_{PC} = 4.6$ Hz), 132.4 (d, $J_{PC} = 22.7$ Hz), 132.3, 130.4, 129.9 (d, $J_{PC} = 3.0$ Hz), 129.0 (d, $J_{PC} = 25.5$ Hz), 128.7, 128.5 (d, $J_{PC} = 45.9$ Hz), 128.5, 128.1, 121.8 (d, $J_{PC} = 28.0$ Hz), 120.4, 119.4, 119.0, 111.9, 26.7 ppm. Elemental analysis (%) calcd for C₄₃H₂₈NOP: C, 85.27; H, 4.66; Found: C, 85.34; H, 4.15. HRMS+pESI (m/z) [M+H]⁺ Calcd.: 606.19868, Found: 606.19740.

[5-(4-cyanophenyl)-3-fluorананthenyl]diphenyl phosphinate (8d) A few amount of the phosphinate 6a was obtained in the course of the crystallisation attempts of 6, under air. ¹H NMR (500 MHz, CDCl₃), δ: 7.85 (d, $J = 7.2$ Hz, 1H), 7.79 (d, $J = 6.6$ Hz, 1H), 7.70 (d, $J = 7.0$ Hz, 1H), 7.62 (d, $J = 7.8$ Hz, 1H), 7.51–7.46 (m, 3H), 7.43 (q, $J = 7.4$ Hz, 6H), 7.33–7.23 (m, 7H), 7.17 (d, $J = 7.8$ Hz, 2H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: 31.9 ppm.

[5-(4-cyanophenyl)-3-fluorананthenyl]diphenyl phosphine oxide (8e) In a Schlenk tube charged with [5-(4-cyanophenyl)-3-fluorананthenyl]diphenyl phosphine (6) (0.05 mmol, 1 equiv), H₂O₂ (excess) into dichloromethane (0.025 M, 2 mL). The solution was stirred at room temperature overnight before extraction (dichloromethane / water). The organic layer was removed in vacuum to give the oxide phosphine. ¹H NMR (500 MHz, CDCl₃), δ: 7.91–7.85 (m, 3H), 7.80 (d, $J = 7.2$ Hz, 1H), 7.64 (d, $J = 7.2$ Hz, 1H), 7.61 (dd, $J = 7.9$, 5.1 Hz, 2H), 7.50–7.41 (m, 4H), 7.38 (t, $J = 6.7$ Hz, 1H), 7.36–7.31 (m, 8H), 7.29 (d, $J = 7.2$ Hz, 1H), 7.22 (d, $J = 8.2$ Hz, 2H), 7.11 (d, $J = 8.2$ Hz, 2H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: 30.9 ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 146.1, 141.9 (d, $J_{PC} = 2.8$ Hz), 140.1 (d, $J_{PC} = 4.6$ Hz), 140.0 (d, $J_{PC} = 4.6$ Hz), 139.5, 138.2 (d, $J_{PC} = 15.1$ Hz), 135.1, 134.3, 134.1, 134.0, 133.4, 132.7, 131.7, 131.5 (d, $J_{PC} = 2.8$ Hz), 131.2 (d, $J_{PC} = 9.2$ Hz), 130.6, 129.7 (d, $J_{PC} = 7.4$ Hz), 129.4, 128.6, 128.5, 128.3, 128.1, 122.3, 121.6, 120.2, 119.4, 118.6 (d, $J_{PC} = 4.2$ Hz), 118.1, 111.3, 110.3 ppm. Elemental analysis (%) calcd for C₃₅H₂₂NOP: C, 83.49; H, 4.40; Found: C, 84.19; H, 4.45. HRMS+pESI (m/z) [M+Na]⁺ Calcd.: 526.13367, Found: 526.13368.

[[3-cyano]-6-fluorананthenyl]phenyldiphenyl phosphine (8f) ¹H NMR (500 MHz, CDCl₃), δ: 7.95 (d, $J = 6.8$ Hz, 1H), 7.91 (d, $J = 7.4$ Hz, 1H), 7.67 (dd, $J = 10.1$, 7.7 Hz, 4H), 7.59–7.53 (m, 1H), 7.37 (dt, $J = 15.4$, 7.5 Hz, 10H), 7.28 (dd, $J = 12.8$, 7.0 Hz, 6H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: -11.4 (s) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 144.7, 144.5, 143.8 (d, $J_{PC} = 7.0$ Hz), 139.6, 138.9, 137.2 (d, $J_{PC} = 5.6$ Hz), 137.1 (d, $J_{PC} = 19.9$ Hz), 136.2 (d, $J_{PC} = 3.5$ Hz), 134.0 (d, $J_{PC} = 28.9$ Hz), 132.6, 132.0 (d, $J_{PC} = 28.9$ Hz), 131.9 (d, $J_{PC} = 9.5$ Hz), 131.5, 129.4 (d, $J_{PC} = 6.6$ Hz), 129.0, 128.8 (d, $J_{PC} = 6.7$ Hz), 128.7 (d, $J_{PC} = 6.8$ Hz), 128.2 (d, $J_{PC} = 12.3$ Hz), 125.4 (d, $J_{PC} = 40.58$ Hz), 124.1, 121.9 (d, $J_{PC} = 7.8$ Hz), 121.0, 119.1, 111.6. Elemental analysis (%) calcd for C₃₅H₂₂NP: C, 86.23; H, 4.55; Found: C, 86.45; H, 4.68. HRMS+pESI (m/z) [M+Na]⁺ Calcd.: 510.13821, Found: 510.13953.

### 1-(4-cyanophenyl)-fluorананthenyl (8g)

¹H NMR (500 MHz, CDCl₃), δ: 7.98 (t, $J = 7.4$ Hz, 2H), 7.93 (t, $J = 3.0$ Hz, 2H), 7.81 (dd, $J = 8.5$, 2.3 Hz, 3H), 7.71 (d, $J = 8.5$ Hz, 2H), 7.65 (dd, $J = 8.5$, 6.8 Hz, 1H), 7.59 (d, $J = 7.0$ Hz, 1H), 7.42 (dd, $J = 5.1$, 3.6 Hz, 2H) ppm.

**Rhodium complex stabilized by 3-(diphenylphosphino)fluoranthene (12)** In a Schlenk tube equipped with a magnetic stirring bar was charged with 3-(diphenylphosphine)fluoranthene (1 equiv, 0.131 mmol, 50.4 mg), the dimeric rhodium [RhCl₂Cp*]₂ (0.5 equiv, 0.066 mmol,
40.8 mg), degassed before addition of distilled dichloromethane (0.026 M, 5 ml). The mixture was stirred at room temperature under argon overnight before removing the solvent in vacuum to give the corresponding rhodium. The redish solid was further purified by crystallization using a dichloromethane solution and slow addition of heptane. ¹H NMR (500 MHz, CDCl₃), δ: 8.17 (d, *J* = 8.5 Hz, 1H), 7.89 (q, *J* = 8.0 Hz, 4H), 7.84 (d, *J* = 6.9 Hz, 2H), 7.68 (dd, *J* = 13.6, 7.5 Hz, 2H), 7.44–7.36 (m, 6H), 7.25 (d, *J* = 5.7 Hz, 3H), 7.19–7.17 (m, 1H), 1.28 (s, 15H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: 30.5 (d, *J* = 144.3 Hz). ¹³C NMR (125 MHz, CDCl₃), δ: 140.9, 140.3, 138.4, 137.8 (d, *J*<sub>PC</sub> = 1.2 Hz), 137.7, 137.5, 133.1, 133.0, 131.7, 131.6, 129.6 (d, *J*<sub>PC</sub> = 3.6 Hz), 129.0, 128.6, 128.5, 128.3, 128.0, 122.3, 121.7, 121.0, 118.6 (d, *J*<sub>PC</sub> = 11.6 Hz), 99.3, 9.1 ppm. Elemental analysis (%) calcd for C₃₈H₃₄Cl₂PrH: C, 65.63; H, 4.93; Found: C, 65.29; H, 4.82. HRMS+pESI (m/z) [M-Cl]+ Calcd.: 659.11362, Found: 659.11277.

**Rhodacycle with 3-(diphenylphosphino)-fluoranthene (13)** In a Schlenk tube equipped with a magnetic stirring bar was charged with 3-(diphenylphosphine)fluoranthene (1 equiv, 0.131 mmol, 50.4 mg), the dimeric rhodium [RhCl₂Cp*]₂ (0.5 equiv, 0.066 mmol, 40.8 mg), KOAc (4 equiv, 0.264 mmol, 25.9 mg), degassed before addition of distilled CH₂Cl₂ (0.026 M, 5 ml). The mixture was stirred at room temperature under argon overnight before removing the solvent in vacuum to give the corresponding rhodium. The reddish solid was further purified by crystallization using a dichloromethane solution and slow addition of heptane. ¹H NMR (500 MHz, CDCl₃), δ: 8.26–8.18 (m, 2H), 7.95 (d, *J* = 2.7 Hz, 1H), 7.94 (s, 1H), 7.88 (d, *J* = 5.4 Hz, 2H), 7.86–7.81 (m, 2H), 7.55–7.51 (m, 3H), 7.37 (t, *J* = 7.5 Hz, 1H), 7.30 (q, *J* = 7.6 Hz, 2H), 7.27–7.21 (m, 2H), 6.99–6.91 (m, 2H), 1.58 (d, *J* = 3.0 Hz, 15H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: 65.9 (d, *J* = 163.1 Hz) ppm. ¹³C NMR (125 MHz, CDCl₃), δ: 170.4 (dd, *J*<sub>PC</sub> = 32.5 and 8.9 Hz), 148.4 (d, *J*<sub>PC</sub> = 37.3 Hz), 141.2, 140.2 (dd, *J*<sub>PC</sub> = 248.3 and 2.0 Hz), 137.4 (d, *J*<sub>PC</sub> = 46.3 and 2.6 Hz), 136.5 (d, *J*<sub>PC</sub> = 13.2 and 0.8 Hz), 135.8, 135.8, 132.3 (d, *J*<sub>PC</sub> = 9.9 Hz), 131.9 (d, *J*<sub>PC</sub> = 18.1 Hz), 131.2 (d, *J*<sub>PC</sub> = 4.6 Hz), 130.4, 130.0 (d, *J*<sub>PC</sub> = 2.3 Hz), 129.3 (d, *J*<sub>PC</sub> = 45.0 Hz), 129.1, 128.5 (d, *J*<sub>PC</sub> = 35.4 and 10.5 Hz), 128.3, 127.9, 126.2, 122.8, 122.0, 121.1, 119.7 (d, *J*<sub>PC</sub> = 7.7 Hz), 100.1 (dd, *J*<sub>PC</sub> = 4.9 and 4.9 Hz), 9.26 ppm. Elemental analysis (%) calcd for C₃₈H₃₃ClPrH: C, 69.15; H, 5.19; Found: C, 69.58; H, 5.39. HRMS+pESI (m/z) [M-Cl]⁺ Calcd.: 623.13694, Found: 623.13859.

**Rhodacycle (16)** The rhodacycle was isolated in a few amount as a resting-state during the synthesis of the compound [5-(4-acetylphenyl)-3-fluororanthenyl]diphenyl phosphine (10b). ¹H NMR (500 MHz, CDCl₃), δ: 8.00–7.95 (m, 2H), 7.86 (dt, *J* = 20.0, 7.9 Hz, 8H), 7.63 (dd, *J* = 21.7, 7.0 Hz, 2H), 7.47 (d, *J* = 7.2 Hz, 1H), 7.41–7.27 (m, 8H), 7.15 (dd, *J* = 8.3, 2.6 Hz, 1H), 7.03–6.97 (m, 4H), 6.91 (dd, *J* = 16.0, 7.6 Hz, 2H), 6.81 (dt, *J* = 14.3, 7.5 Hz, 3H), 6.44–6.38 (m, 3H), 6.24 (t, *J* = 8.7 Hz, 2H), 6.17 (d, *J* = 9.0 Hz, 1H), 6.03 (t, *J* = 8.5 Hz, 2H), 2.52 (s, 3H) ppm. ³¹P{¹H} NMR (202 MHz, CDCl₃), δ: 41.5 (dd, ¹JₚRh = 85 Hz and ²JₚP = 20 Hz, 1P), 40.2 (dd, ¹JₚRh = 85 Hz and ²JₚP = 20 Hz, 1P) ppm. HRMS+pESI (m/z) [M-Cl]+ Calcd.: 1071.10221 Found: 1071.10190.

**Computational details.** Quantum mechanics calculations were performed with the Gaussian16 software package.²⁰ Energies were computed by density functional theory with the global hybrid M06-2X exchange-correlation functional,²¹ with def2-SVP basis set²² using experimental X-Ray geometries. Non Covalent

Interactions were computed and visualized using NCIPLOT²³ and IGMPLOT.²⁴ All NCI surfaces were plotted with an isovalue of 0.006 a.u. Electron localization function (ELF) topological analysis were performed with the TopChem2 package version 3.²⁵ The ELF basins and NCI surfaces have been plotted with VMD software.²⁶

## Acknowledgements

This work was supported by the CNRS, the Université Bourgogne Europe, the Conseil Régional Bourgogne Franche-Comté and the Fonds Européen de Développement Régional (FEDER). This work was also funded by the French Agence Nationale de la Recherche via the ANR-JCJC program 2018 FIT-FUN (ANR-18-CE07-0015, for RJ and CS) and ANR-PRC program 2020 CARAPH (ANR-20-CE07-0001-01, for JCH). Thanks is due to the PACSMUB platform for analyses (SATT SAYENS) especially Q. Bonnin and T. Regnier. Calculations were performed using HPC resources from DSI-CCUB (Université de Bourgogne, for PFL).

**Keywords:** C–H Activation • Rhodacycle • Phosphine design • Phosphorus migration • X-ray analysis

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