The Oxidation of Hydrazobenzene Catalyzed by Cobalt Complexes in Nonaqueous Solvents

摘要

The oxidation of hydrazobenzene by molecular oxygen in the polar solvent methanol is catalysed by a Schiff`s base complex Co(3MeOsalen) which is a synthetic oxygen carrier. The products are trans-azobenzene and water. The rate of the reaction has been studied spectrophotometrically and the rate law established. A mechanism involving a ternary complex of catalyst, hydrazobenzene and molecular oxygen has been proposed. The kinetic studies show that a ternary complex CoL·H₂AB·O₂ is involved in the rate determining step. The reactions are summarised in a catalytic cycle. The kinetic data suggest that a ternary complex involving Co (3MeOsalen), triphenyl-phosphine and molecular oxygen is catalytically acive species but at higher triphenylphosphine concentrations the catalyst becomes inactive. The destruction of the catalytic activity could be due to the catalyst becoming coordinated with triphenyl phosphine at both z axis sites of the complex e.g. Co (3MeOsalen)(PPh₃)₂.