Oxidation of Toluene by Cobalt(III)-Ligand Effects

Abstract

Cobaltic carboxylates oxidize toluene via a reversible one electron transfer process in acetic acid solution in the absence of oxygen. Lingands of cobaltic ion were found to have a very important role in the oxidation reaction. So we investigated the effect of ligands of cobaltic io n. NeutraI Iigands affectedonIy the activity Co(III)but anion ligands affected both reaction rates and reaction products. Strongly coordinated neutral ligands such as bipyridyl, pyridine or acetonitrile reduced the reduction rate of Co(III)(Table 1, Fig.6). Large anion ligands such as iso-butyric or pelargonic anion suppressed the oxidation by the reversible one electron transfer and were favourable to decarboxylation (Table 4).Accordingly, the effect of ligands on the aromatic oxydation by Co(III)can be attributed to the steric factor rather than to the redox factor, and the rate determing step may be inner sphere complex fermation between toluene and cobaltic ion in one electron transfer process,