Transition metal–carbon bonds. Part XVIII. Allylic and related complexes of palladium derived from hexamethyl Dewar benzene

Abstract

Hexamethyl Dewar benzene complexes of palladium of the type [PdX₂(C₁₂H₁₈)](X = Cl or Br) are described in which the hexamethyl Dewar benzene is acting as a chelating diolefin. These complexes react with sodium methoxide in methanol to give halogen-bridged complexes of the type [Pd₂X₂(C₁₂H₁₇)₂] in which the ligand C₁₂H₁₇ still retains the carbon framework of hexamethyl Dewar benzene but acts as a π-allylic ligand. Various derivatives of the type [PdXL(C₁₂H₁₇)](L = PPh₃, AsPh₃, PMe₂Ph, or isoquinoline) and [PdY(C₁₂H₁₇)](Y = acetylacetonate or C₅H₅) are described. I.r. and n.m.r. spectroscopic data are given. Complexes of the type [Pd₂X₂(C₁₂H₁₇)₂] react with PMe₂Ph (1–2 mol. per Pd atom) to cause magnetic equivalence of the allylic hydrogens via a σ-allylic complex.