Reductive elimination of aryl carboxylates from acyl(aryloxy)nickel(II) and -palladium(II) complexes

Article abstract of DOI:10.1021/om00125a033

Acyl(p-cyanophenoxy)nickel(II) and -palladium(II) complexes, M(COR)(OC₆H₄-p-CN)L₂ (M = Ni, Pd; L₂ = bpy, (PEt₃)₂), have been prepared by insertion reactions of CO into the metal-carbon bonds of the corresponding methylnickel(II) and -palladium(II) complexes. Addition of π-acids such as CO, maleic anhydride, and acrylonitrile selectively induces reductive elimination of p-cyanophenyl acetate from acylnickel(II) complexes, whereas thermolysis of the complexes mainly results in decarbonylation. In contrast, reductive elimination from the palladium analogue proceeds smoothly on thermolysis, and no apparent accelerating effect of added π-acids is observed. Kinetic studies of both reductive eliminations reveal that the former proceeds via an associative mechanism involving a five-coordinate intermediate, whereas the latter proceeds via two mechanisms, one being a dissociative pathway involving a three-coordinate species and the other being a direct reductive elimination from a four-coordinate species.