ORGANOCOBALOXIMES - SYNTHESIS, OXYGEN INSERTION AND KINETICS

A total of 27 organocobaloximes have been synthesised and characterize d with three different dioxime ligands, dmgH, chgH and dpgH. Many of t he chgH and all the dpgH complexes have been synthesised for the first time. The insertion of molecular oxygen into these organocobaloximes, RCoIII(L-2)B [L = dmgH, chgH and dpgH) under thermal and photochemica l conditions have been studied. Kinetic studies at ambient temperature under irradiation show that the rate of insertion depends upon the na ture of R, L, B and the solvent. The rate follows the order dpgH > chg H > dmgH; Naphthyl > heteroaromaticmethyl > benzyl; piperidine > morph oline > gamma-picoline > pyridine > 2-bromopyridine > 2-acetylpyridine ; and the rates are faster in acetonitrile than in acetone and chlorof orm. In methanol, the benzylic cobaloximes exist as an equilibrium mix ture of solvated penta-coordinated and hexa-coordinated species and in chloroform these exist as hexa-coordinated species. (C) 1998 Elsevier Science S.A. All rights reserved.