Synthesis, structure and cytotoxicity studies of four-coordinate bis (cis-bis(diphenylphosphino)ethene) gold(I) complexes, [Au(dppey)(2)]X.

Four-coordinate 1:2 gold(I) complex salts with cis-bis(diphenylphosphino)ethene, [Au(dppey)(2)]X have been synthesized for X=PF(6)(-), CF(3)SO(3)(-), BF(4)(-), Cl(-), Br(-) and BPh(4)(-) and characterized by NMR spectroscopy and electrospray mass spectrometry. Single crystal X-ray structure determinations show the BF(4)(-), Cl(-) and Br(-) complexes to be isostructural, although with different degrees of hydration, while the BPh(4)(-) complex crystallizes as an acetone solvate with two molecules in the asymmetric unit. The Au(P-P)(2) core for the BF(4)(-), Cl(-) and Br(-) complexes adopts D(2) symmetry with Au-P bond lengths 2.3980(7)-2.4009(7) A and inter-ligand P-Au-P angles 114.78(2)-127.82(2)) degrees . The Au(P-P)(2) core in the BPh(4)(-) complex is unsymmetrical with Au-P bond lengths 2.364(1)-2.420(1) A and inter-ligand P-Au-P angles 104.76(5)-137.50(4) degrees . In vitro cytotoxicity studies show the PF(6)(-), CF(3)SO(3)(-), BF(4)(-), Cl(-), Br(-) and I(-) complexes to be potent and selective growth inhibitors of the human cell lines MCF7 (hormone-dependent breast cancer), MDA-MB-231 (hormone-independent breast cancer), MM96L (melanoma), CI80-13S (cisplatin resistant ovarian cancer) and a normal cell line NFF (neonatal foreskin fibroblasts), achieving IC(50) values between 13 and 196nM. The halogen and triflate salts were approximately twice as potent towards the MCF7 and MDA-MB-231 cell lines compared to the PF(6)(-) and BF(4)(-) derivatives; while the cytotoxicity of all complexes towards the sensitive CI80-13S and MM96L cancer cell lines was approximately 10-fold greater than that displayed towards the normal human cell line (NFF).