Methyl for halogen exchange reactions between palladium(II), platinum(II), gold(I), and gold(III) complexes

Abstract

A series of reactions in which methyl and halogen groups are exchanged between gold(I), gold(II), palladium(II), and platinum(II) centres has been studied. It is proposed that the exchange reactions proceed by the S_E2(cyclic) mechanism, in order to rationalise the observations that cleavage of the Pt–Me bond in cis-[PtMe₂(PMe₂Ph)₂] by various metal halides follows the reactivity series [Aul(PMe₂Ph)] > [AuBr(PMe₂Ph)] > [AuCl(PMe₂Ph)]; [Ptl₂(PMe₂Ph)₂][PtCl₂(PMe₂Ph)₂]; [AuCl(PMe₂Ph)] > cis-[PdCl₂(PMe₂Ph)₂]cis[PtCl₂(PMe₂Ph)₂], that the rate of methylation reactions using [MeAu(PMe₂Ph)] as methylating agent is much greater than for cis-[PtMe₂(PMe₂Ph)₂], and that the reaction of cis-[PtMe₂(PMe₂Ph)₂] with cis-[PtCl₂(PMe₂Ph)₂] gives cis-[PtCl(Me)(PMe₂Ph)₂] as the product of kinetic control. The methylating power of various methylmetal complexes follows the series cis-[PtMe₂(PMe₂Ph)₂], [AuMe(PMe₂Ph)] > [AuMe₃(PMe₂Ph)]trans-[MCl(Me)-(PMe₂Ph)₂](M = Pd or Pt), cis-[AuX(Me)₂(PMe₂Ph)](X = halogen).