Synthesis and In Vitro (Anticancer) Evaluation of eta(6)-Arene Ruthenium Complexes Bearing Stannyl Ligands

Treatment of the known half-sandwich complexes of the type [(eta(6)-C6H6)RuCl2(P(OR)(3))] (R = Me or Ph) with SnCl2 yielded three new half-sandwich ruthenium complexes (C1-C3): [(eta(6)-C6H6)RuCl(SnCl3)(P(OMe)(3))] (C1), [(eta(6)-C6H6)RuCl(SnCl3)(P(OPh)(3))] (C2) and the bis-stannyl complex [(eta(6)-C6H6)Ru(SnCl3)(2)(P(OMe)(3))] (C3) by facile insertion of SnCl2 into the Ru-Cl bonds. Treatment of the known complexes [(eta(6)-C6H6)RuCl(SnCl3)(PPh3)] and [(eta(6)-C6H6)RuCl2(PPh3)] with 4-dimethylaminopyridine (DAMP) and ammonium tetrafluoroborate afforded the complex salts: [(eta(6)-C6H6)Ru(SnCl3)(PPh3)(DAMP)]+BF4- (C4) and [(eta(6)-C6H6)RuCl(PPh3)(DAMP)]+BF4- (C5) respectively. Complexes C1-C5 have been fully characterized by spectroscopic means (IR, UV-vis, multinuclear NMR, ESI-MS) and their thermal behaviour elucidated by thermal gravimetric analysis (TGA). Structural characterization by single crystal X-ray crystallography of the novel complex C2 and [(eta(6)-C6H6)RuCl2(P(OPh)(3))], the latter having escaped elucidation by this method, is also reported. Finally, the cytotoxicity of the complexes was determined on the A2780 (human ovarian cancer), A2780cisR (human ovarian cis-platin-resistant cancer), and the HEK293 (human embryonic kidney) cell lines and discussed, and an attempt is made to elucidate the effect of the stannyl ligand on cytotoxicity.