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 SE2(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).