Selectivity in reactions of alkyl-aryl-transition-metal complexes with electrophiles

Article abstract of DOI:10.1021/ic00131a061

The new methylarylmetal complexes cis-[AuMe₂Ph(PPh₃)], cis-[AuMe₂(4-MeC₆H₄)(PPh₃)], [PtMe(4-MeC₆H₄)(C₈H₁₂)], cis-[PtMePh(PMePh₂)₂], and cis-[PtMe(4-MeC₆H₄)(PMe₂Ph)₂] have been prepared and characterized. In reactions with electrophilic reagents such as HCl, HgCl₂, and [PtI₂(PMe₂Ph)₂], the complexes undergo selective cleavage of a methyl-metal bond (e.g., cis-[PtMePh(PMePh₂)₂]) or an aryl-metal bond (e.g., cis-[AuMe₂Ph(PPh₃)], [PtMe(4-MeC₆H₄)(C₈H₁₂)]). From the selectivity observed and from studies of relative rates of reaction, it is argued that the S_E2 mechanism leads to selective aryl-metal bond cleavage and that a different mechanism, probably involving an oxidative-addition-reductive-elimination sequence, leads to selective methyl-metal bond cleavage.