Amphiphilic bis(thiolato)-nickel(II), -palladium(II) and -platinum(II) complexes with diphosphine or phosphinoarsine ligands

The novel complexes [M(L–L)(H2dmsucc-S,S′)][M = Ni, Pd or Pt; L–L = 1,2-bis(diphenyl-phosphino)ethane, dppe; M = Pd or Pt, L–L = 1-diphenylarsino-2-diphenylphosphinoethane, dadpe; H4dmsucc = dimercaptosuccinic acid) and [Ni(dppe)(Hmsucc)](H3msucc = mercaptosuccinic acid) have been prepared and characterised. The reactions of sodium 2,3-dimercaptopropanesulfonate, sodium 1-thio-β-D-glucopyranosate and dithiothreitol with [M(L–L)X2](M = Ni, Pd or Pt; X = Cl or Br) were investigated by 31P-{1H} NMR spectroscopy. The 31P NMR chemical shifts, 31P–31P and 195Pt–31P coupling constants, and the conformations of chelate rings (derived from 1H–1H coupling constants) in mixed-ligand product from these reactions are discussed. The use of these thiolate ligands has enabled solubilisation of several complexes containing dppe or dadpe ligands in aqueous media. The cytotoxicities of dppe and dadpe complexes of Pd and Pt with dimercaptosuccinic acid were investigated.