Sulphur–arsenic ligands. Dimethyl(methylthio)arsine complexes of halogenotrimethylplatinum(IV) and tricarbonylhalogenorhenium(I)

Abstract

Dimethyl(methylthio)arsine, AsMe₂(SMe)(L), is a potentially ambidentate ligand with the possibility of arsine and/or sulphur co-ordination to a transition metal. We have investigated the reaction of the ligand for the scission of the tetrameric trimethylplatinum halides, and that for carbon monoxide displacement from the rhenium pentacarbonyl halides. In both of these reactions organic arsines and sulphides individually are known to be effective, producing well characterised stable products. Ligand L reacts with [(PtXMe₃)₄](X = Cl, Br, or I) and with [ReX(CO)₅](X = Cl, Br, or I) to yield respectively fac-[PtXMe₃L₂] and fac-[ReX(CO)₃L₂] in good yield. Hydrogen-1 and ¹³C n.m.r. studies demonstrate that in all complexes the ligand behaves in a monodentate manner with exclusively arsenic–metal bonds. In solution the compounds give no indications of any fluxional behaviour in the temperature range –80 to +80°C. The fac structure of all of these complexes gives rise to the interesting observation that all three methyl groups in the co-ordinated ligand AsMe₂(SMe) are non-equivalent.