Mixed Arylolefin/NHC Complexes of Platinum(II): Syntheses, Characterizations, and In Vitro Cytotoxicities

Eight platinum­(II) complexes of the formula [PtCl­(arylolefin)­(NHC)] (2–9) with varying NHCs and arylolefin chelators have been prepared and analyzed by spectroscopic and spectrometric methods. The study reveals that the binding of the arylolefins is influenced by remote ring substituents and by the NHC spectator ligands. A more strongly donating NHC exhibits an increased trans influence and weakens the olefinic donor notably, which could lead to its premature dissociation. Cytotoxicity studies on four human cancer cell lines indicate that a stronger binding of the arylolefin is more beneficial. The highest cytotoxic effects (IC50 = 0.18–0.70 μM) were observed for the complex [PtCl­(Meug)­(IMes)] (3), containing a more weakly donating NHC and the strongest arylolefin donor.