Reaction of electrogenerated square-planar nickel(I) complexes with alkyl halides

Abstract

The electrochemical reduction of the complexes, [NN′-ethylenebis(salicylideneiminato)]nickel(II), [NiL²], and (5,5,7,12,12,14-hexamethyl-1,4,8,11 -tetra-azacyclotetradecane)nickel(II), [NiL¹]²⁺, to the corresponding nickel(I) complexes at a platinum cathode in acetonitrile has been studied. The nickel(I) complexes react rapidly with alkyl bromides and alkyl iodides and, with the exception of the [NiL¹]²⁺-primary alkyl bromide systems, the reaction leads to an alkyl radical and regeneration of the nickel(II) complex. Mence in most cases the electrolysis of alkyl halides in the presence of catalytic quantities of the nickel complexes leads to their complete reduction. It is proposed that the chemical reaction involves an organonickel species and that the overall behaviour of the systems is determined by the lifetime of the nickel–carbon bond.