# The Cytotoxic Activity of Diiron Bis-Cyclopentadienyl Complexes with Bridging C\({}_{3}\)-Ligands
## 4 Experimental  
### Materials and Methods  
Solvents and organic reactants were purchased from Merck or TCI Europe. Compounds **1a**[40], **2b,e**[20,36], **3a**[27], **4a-c**[29] and **5a-b**[29] were synthesized according to the respective literature procedures; once obtained, all the products were stored in air. Chromatography separations were carried out on columns of deactivated alumina (Merck, 4% _w/w_ water), unless otherwise specified. Infrared spectra of solutions were recorded on a Perkin Elmer Spectrum 100 FT-IR spectrometer with a CaF\({}_{2}\) liquid transmission cell (2300-1500 cm\({}^{-1}\) range) and processed with Spectragyph software [41]. NMR spectra were recorded on a Bruker Avance II DRX400 instrument equipped with a BBPO broadband probe. Chemical shifts (expressed in parts per million) are referenced to the residual solvent peaks (\({}^{1}\)H) [42]. NMR signals due to a second isomeric form (where it has been possible to detect them) are italicized. Elemental analyses were performed on a Vario MICRO cube instrument (Elementary). Synthesis of [Fe\({}_{2}\)Cp\({}_{2}\)(CO)(\(\mu\)-CO)(\(\mu\)-\(\eta^{1}\):\(\eta^{3}\)-C\({}^{3}\)(\(R^{\prime}\))C\({}^{2}\)(\(R^{\prime\prime}\))C\({}^{1}\)NMe(\(R\))]JCF\({}_{3}\)SO\({}_{3}\), (**2a,c,d**)  
_General procedure_: A red solution of **1a-b** (ca. 0.15 mmol) and Me\({}_{3}\)NO (ca. 0.30 mmol) in MeOH (5 mL) was treated with the appropriate alkyne (ca. 0.45 mmol), in an open system allowing the release of gaseous products (Me\({}_{3}\)N and CO\({}_{2}\)). The mixture was heated at 45 \({}^{\circ}\)C for ca. 4 h. Conversion was checked by IR spectroscopy and volatiles were removed under vacuum. The residue was dissolved in CH\({}_{2}\)Cl\({}_{2}\) and moved on top of an alumina column (neutral, Brockmann activity I; h 6, d 2.3 cm). Impurities were eluted with CH\({}_{2}\)Cl\({}_{2}\) and THF, then a band was collected using MeCN. The eluate was dried under vacuum and the resulting solid was triturated in Et\({}_{2}\)O. The suspension was filtered; the solid was washed with Et\({}_{2}\)O and dried under vacuum. **[Fe\({}_{2}\)Cp\({}_{2}\)CO)(\(\mu\)-CO)(\(\mu\)-\(\eta^{1}\):\(\eta^{3}\)-C\({}^{3}\)(Ph)C\({}^{2}\)(H)C\({}^{1}\)NMe(Xy)]]CF\({}_{3}\)SO\({}_{3}\) (2a)**[20,37]. From **1a** and phenylacetylene. Brown solid, yield 70%. Anal. Calcd. for C\({}_{31}\)H\({}_{28}\)Fe\({}_{2}\)F\({}_{3}\)NO\({}_{5}\)S: C, 53.55; H, 4.06; N, 2.01. Found: C, 53.42; H, 4.13; N, 1.94. IR (CH\({}_{2}\)Cl\({}_{2}\)): \(\widetilde{\
u}\)/cm\({}^{-1}\) = 2000 vs (CO), 1819s (\(\mu\)-CO), 1628m (C\({}^{2}\)C\({}^{1}\)N). \({}^{1}\)H NMR (acetone-d\({}_{6}\)): \(\delta\)/ppm = 7.90 (d, \({}^{3}\)\({}_{\rm HH}\) \(\approx\) 7.4 Hz), 7.63-7.43 (m, 5 H, Ph); 74.2-7.34 (m), 7.25 (t), 7.17 (d), 7.08 (d) (\({}^{3}\)\({}_{\rm HH}\)\(\approx\) 7.5 Hz, 3 H, C\({}_{6}\)H\({}_{3}\)Me\({}_{2}\)); 5.67, 5.33 (s, 5 H, Cp); 5.38, 5.07 (s, 5 H, Cp); 5.13, 4.28 (s, 1 H, C\({}^{2}\)H); 4.42, 3.74 (s, 3 H, NMe); _2.60, 2.33, 2.08_, 1.88 (s, 6 H, C\({}_{6}\)H\({}_{3}\)Me\({}_{2}\)). Cis-E/cis-Z ratio ca. 2:1. **[Fe\({}_{2}\)Cp\({}_{2}\)(CO)(\(\mu\)-CO)(\(\mu\)-\(\eta^{1}\):\(\eta^{3}\)-C\({}^{3}\)(Me)C\({}^{2}\)(H)C\({}^{1}\)NMe\({}_{2}\))]CF\({}_{3}\)SO\({}_{3}\) (2c)**[20,23]. From **1b** and propyne (THF solution ca. 1 mol/L). Brown solid, yield 90%. Anal. Calcd. for C\({}_{19}\)H\({}_{20}\)F\({}_{3}\)Fe\({}_{2}\)NO\({}_{5}\)S: C, 42.02; H, 3.71; N, 2.58; S, 5.90. Found: C, 42.11; H, 3.61; N, 2.68; S, 5.80. IR (CH\({}_{2}\)Cl\({}_{2}\)): \(\widetilde{\
u}\)/cm\({}^{-1}\) = 1990 vs (CO), 1806s (\(\mu\)-CO), 1685m (C\({}^{2}\)C\({}^{1}\)N). \({}^{1}\)H NMR (acetone-d\({}_{6}\)): \(\delta\)/ppm = 5.50 (s, 5 H, Cp); 5.18 (s, 5 H, Cp); 4.59 (s, 1 H, C\({}^{2}\)H); 3.95, 3.94 (s, 6 H, NMe + C\({}^{3}\)Me), 3.33 (s, 3 H, NMe). Cis isomer. **[Fe\({}_{2}\)Cp\({}_{2}\)(CO)(\(\mu\)-CO)(\(\mu\)-\(\eta^{1}\):\(\eta^{3}\)-C\({}^{3}\)(2-naphthyl)C\({}^{2}\)(H)C\({}^{1}\)NMe\({}_{2}\))]CF\({}_{3}\)SO\({}_{3}\) (2d)**[20]. From **1b** and 1-ethynylnaphthalene. Dark-green solid, yield 88%. Anal. Calcd.