Electron transfer oxidation of organic compounds. Part III. Oxidation of cyclohexanone by the hexachloroiridate(IV) anion and by related species

Abstract

Evidence is presented from kinetic and product studies that the first step in the one-equivalent oxidation of the enol of cyclohexanone by the hexachloroiridate(IV) anion is an outer-sphere electron transfer which gives rise to the hexachloroiridate(III) anion and a 2-oxocyclohexyl radical. The latter then reacts with a further iridate(IV) ion by an inner-sphere (i.e., ligand transfer) mechanism, to give 2-chlorocyclohexanone and aquopentachloroiridate(III). Oxygen and acrylonitrile can both compete with iridium(IV) for the free radical. The oxidations of cyclohexanone by aquopentachloro-, diaquotetrachloro-, and hexabromo-iridate(IV) are very similar to the oxidation by hexachloroiridate(IV). The redox potentials of the complexes involved have been redetermined.