Synthesis and in vitro anticancer studies of arene ruthenium(II) and arene osmium(II) complexes bearing arsine and stibine co-ligands on breast cancer cell-lines

We report the synthesis and full characterisation of piano-stool triphenylstibine and triphenylarsine arene complexes of the type: [MCl2(ƞ6-p-cymene)(EPh3)] (E = As, Sb) and [MCl(ƞ6-arene)(EPh3)(SnCl3)] (M = Ru, Os; E = As, Sb; arene = benzene, p-cymene); Ph = C6H5) and their in vitro cytotoxic evaluation on two breast cancer cell lines: MCF-7, MDA-MB-231 and MCF-12A. The compounds were synthesized via a facile two-step reaction: first, the cleavage of the corresponding dimer [(MCl2(ƞ6-arene))2] (M = Ru, Os; arene = benzene, p-cymene) by either: AsPh3 or:SbPh3 to yield the mononuclear dichloride complexes [MCl2(ƞ6-arene)(EPh3)] (M = Ru, Os; E = As, Sb; arene = benzene, p-cymene) 2: (M = Os, E = Sb, arene = p-cymene), 3: (M = Os, E = As, arene = p-cymene); and the known complexes 6: (M = Ru, E = Sb, arene = p-cymene), 7: (M = Ru, E = As, arene = p-cymene), 8: (M = Ru, E = Sb, arene = benzene) and 9: (M = Ru, E = As, arene = benzene). Using these dichloride complexes as starting materials, SnCl2 was inserted into the M-Cl bond to form the chiral trichlorostannyl complexes [MCl(ƞ6-arene)(EPh3)(SnCl3)] (M = Ru, Os; E = As, Sb; arene = benzene, p-cymene) 4: (M = Os, E = Sb, arene = p-cymene), 5: (M = Os, E = As, arene = p-cymene), 10: (M = Ru, E = Sb, arene = p-cymene), 11: (M = Ru, E = As, arene = p-cymene), 12: (M = Ru, E = Sb, arene = benzene), and 13: (M = Ru, E = As, arene = benzene) respectively. The complexes were characterized spectroscopically by means of 1H, 13C{1H} NMR, FTIR, MP, UV–Visible and ESI-MS. The single crystal X-ray diffraction analysis of complex 2 and 10 is also reported revealing the expected piano-stool geometry at the metal centre. The in vitro activity of the complexes on the MCF-7, MDA-MB-231 and the non-tumorigenic cell-line MCF-12A are reported and compared to cisplatin as a positive control. Several tin containing complexes (4, 5, 10 and 12) show remarkable activity and selectivity outperforming cisplatin on both cancer cell-lines with the ruthenium complexes being the most active overall in this series of compounds. One of the most active complexes, 10 was also subjected to ToF-SIMS and the results of this study are reported.