Synthesis and In Vitro (Anticancer) Evaluation of η6-Arene Ruthenium Complexes Bearing Stannyl Ligands

Treatment of the known half-sandwich complexes of the type [(η6-C6H6)RuCl2(P(OR)3)] (R = Me or Ph) with SnCl2 yielded three new half-sandwich ruthenium complexes (C1–C3): [(η6-C6H6)RuCl(SnCl3)(P(OMe)3)] (C1), [(η6-C6H6)RuCl(SnCl3)(P(OPh)3)] (C2) and the bis-stannyl complex [(η6-C6H6)Ru(SnCl3)2(P(OMe)3)] (C3) by facile insertion of SnCl2 into the Ru–Cl bonds. Treatment of the known complexes [(η6-C6H6)RuCl(SnCl3)(PPh3)] and [(η6-C6H6)RuCl2(PPh3)] with 4-dimethylaminopyridine (DAMP) and ammonium tetrafluoroborate afforded the complex salts: [(η6-C6H6)Ru(SnCl3)(PPh3)(DAMP)]+BF4− (C4) and [(η6-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 [(η6-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