Unexpected participation of nucleophiles in the reaction of palladium(II) acetate with divalent 3d metals

The kinetics of reactions of palladium(II) acetate with cobalt(II), nickel(II), and copper(II) acetates were studied by spectrophotometry. These reactions produce heterobimetallic complexes Pd-II(mu-OOCMe)(4)M-II(OH2)(HOOCMe)(2), where M = Co, Ni, or Cu. These reactions are very slow in carefully dehydrated (< 0.01% H2O) acetic acid, but are considerably enhanced by water or acetonitrile. Our data indicate that the activation of the kinetically inert ring structure of the initial palladium complex Pd-3(mu-OOCMe)(6) by means of the nucleophilic attack of an H2O or acetonitrile molecule is the key step of the reaction mechanism.