Palladium(II), platinum(II) and gold(I) complexes containing chiral diphosphines of the Josiphos and Walphos families - Synthesis and evaluation as anticancer agents

A series of palladium(II) and platinum(II) complexes ([PdCl ₂(J003)] (1), [PdCl ₂(W001)] (2), [PtCl ₂(J003)] (3) and [PtCl ₂(W001)] (4), where J003 = the Josiphos ligand (R)-1-[(S)-2-diphenylphosphino)ferrocenyl]ethyldicyclohexylphosphine and W001 = the Walphos ligand (R)-1[(R)-2-(2′-diphenylphosphinyl)ferrocenyl] ethyldo(bis-3,5-trifluoromethylphenyl)phosphine), were prepared from the reaction of the diphosphine ligands with [PdCl ₂(NCMe) ₂] or [PtCl ₂(cod)] and characterised by multinuclear NMR spectroscopy, mass spectrometry and elemental analyses. Single crystal X-ray structures were used to confirm the proposed structures. Attempts to use the same ligands to prepare isoelectronic d ⁸ Au(III) analogues of the palladium and platinum complexes resulted in the reduction of Au(III) to Au(I) and isolation of the Au(I) complexes [AuCl(J003)] (5), [Au ₂Cl ₂(J003)] (6) and [Au ₂Cl ₂(W001)] (7). The cytotoxicity of the four chiral, bidentate ferrocenylphosphine palladium and platinum complexes was investigated against HeLa cells and were found to have low to moderate cytotoxicity. In general, the two Josiphos complexes showed better cytotoxicity compared to the Walphos complexes, irrespective of the metal used.