Reactions of 1,2-dicarbonyls with metallic copper under argon and dioxygen. Oxidative C–C bond scission by metallic copper

Abstract

1,2-Diketones such as benzil, 2,2′-furil, and di(2-pyridyl) diketone react with metallic copper in pyridine under argon by electron transfer from the copper to the 1,2-diketones, giving semidionato copper(I) and µ-enediolato-dicopper(I) complexes in low equilibrium concentrations as detected by e.s.r. and visible absorption spectra. Under dioxygen with a 1 : 1 stoicheiometry of copper to 1,2-diketones, a facile oxidative C–C bond cleavage occurs to give well defined carboxylate copper(II) complexes with ligands such as pyridine, 2,2′-bipyridine, and NNN′N′-tetramethylethylenediamine.