EFFECT OF LIGAND AND SOLVENT ON CHLORIDE-ION COORDINATION IN ANTITUMOR COPPER(I) DIPHOSPHINE COMPLEXES - SYNTHESIS OF [CU(DPPE)(2)]CL AND ANALOGOUS COMPLEXES (DPPE = 1,2-BIS(DIPHENYLPHOSPHINO)ETHANE)

Complexes formed between copper(I) and 1,2-bis(diphenylphosphino)ethan e (L-1) have previously been isolated. as salts of the [CuL21](+) cati on if only non-coordinating anions are present, or as [Cu2Cl2L31] if c hloride is present. We describe the synthesis of [CuL21] the stoichiom etry of which is confirmed by elemental analysis, FAB mass spectroscop y and conductivity. Polar solvents (water-ethanol mixtures) lead to is olation of the latter, whereas solvents of lower polarity (CHCl3, CH2C l2) lead to isolation of the complexes containing coordinated chloride . Related ligands such as cis-1,2-bis(diphenylphosphino) ethene, 1,2-b is(diethylphosphino) ethane, 1,2-bis(dimethylphosphino) ethane and 1,2 -bis(hydroxymethylphosphino) ethane, give salts [CuL2]Cl. This behavio ur, and that of other 1,2-bisphosphine ligands, is rationalised in ter ms of competition between chloride and phosphine ligands for binding s ites on the metal with the equilibrium position determined by solvent polarity, ligand structure and rigidity, and steric and electronic pro perties of the ligands. (C) 1998 Elsevier Science Ltd.