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

Abstract

Four-coordinate 1:2 gold(I) complex salts with cis-bis(diphenylphosphino)ethene, [Au(dppey)2]X have been synthesized for X = PF6-, CF3SO3-, BF4-, Cl-, Br- and BPh4- and characterized by NMR spectroscopy and electrospray mass spectrometry. Single crystal X-ray structure determinations show the BF4-, Cl- and Br- complexes to be isostructural, although with different degrees of hydration, while the BPh4- complex crystallizes as an acetone solvate with two molecules in the asymmetric unit. The Au(P-P)2 core for the BF4-, Cl- and Br- complexes adopts D2 symmetry with Au-P bond lengths 2.3980(7)-2.4009(7) Šand inter-ligand P-Au-P angles 114.78(2)-127.82(2))஠The Au(P-P)2 core in the BPh4- complex is unsymmetrical with Au-P bond lengths 2.364(1)-2.420(1) Šand inter-ligand P-Au-P angles 104.76(5)-137.50(4)஠In vitro cytotoxicity studies show the PF6-, CF3SO3-, BF4-, 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 IC50 values between 13 and 196 nM. The halogen and triflate salts were approximately twice as potent towards the MCF7 and MDA-MB-231 cell lines compared to the PF6- and BF4- 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).