Gold(I) complexes of 1-diphenylarsino-2-diphenylphosphinoethane (dadpe): solution studies, X-ray crystal structures, and cytotoxicity of [(AuCl)2dadpe]·0.5dma (dma = dimethylacetamide) and [Au(dadpe)2]Cl·2H2O

Abstract

The complexes [(AuCl)₂dadpe](1) and [Au(dadpe)₂]Cl (2) where dadpe is Ph₂PCH₂CH₂AsPh₂ have been prepared and characterized by n.m.r. spectroscopy (³¹P-{¹H}, ¹H, and ¹³C-{¹H}) and by X-ray crystallography. ³¹P-{¹H} N.m.r. spectroscopy shows that complex (1) is converted into (2) on titration with dadpe in CDCl₃ at a Au: dadpe ratio of 1:2. At higher ratios there is exchange between complex (2) and the excess of ligand. Such rapid ligand exchange is also indicated by the ¹H n.m.r. data. Crystals of (1) are monoclinic, space group Cc with a= 19.385(3), b= 11.011(2), c= 27.260(1)Å, β= 96.40(1)°, and Z= 8. The ligand co-ordinates two AuCl chains with intermolecular Au ⋯ Au contact of 3.21 Å. The P and As atoms are disordered and there appears to be conformational flexibility about the ethane bridge. Crystals of (2) are monoclinic, space group P2₁/n, a= 10.192(1), b= 21.797(7), c= 21.683(10)Å, β= 94.14(3)°, and Z= 4 and contain bis chelated Au^I in a distorted-tetrahedral environment; again the P and As atoms are disordered. Complexes (1) and (2) are significantly more toxic towards L1210, WS, and V.79 cells in vitro than is the free ligand, dadpe, and are comparable to [Au(dppe)₂]Cl in their toxicity towards WS and V.79 cell lines.