ELECTROCHEMICAL OLEFIN EPOXIDATION WITH MANGANESE MESO-TETRAPHENYLPORPHYRIN CATALYST AND HYDROGEN-PEROXIDE GENERATION AT POLYMER-COATED ELECTRODES

An electrocatalytic reaction for olefin epoxidation is presented. Hydrogen peroxide is generated electrochemically by reduction of dioxygen in methylene chloride solvent containing benzoic acid as proton source, [Mn(TPP)Cl] as catalyst, 1-methylimidazole as axial base, and olefin as substrate. The glassy-carbon electrode is coated with a 20–80-nm film of poly-[Ru(vbpy)3]2+, which has high permeability to dioxygen and very low permeability to porphyrin. The polymer film prevents electrochemical reduction of the high-valent metal oxo porphyrin [Mn(=O)TPP]. At high concentrations of olefin and porphyrin, the electrocatalytic reaction runs at nearly 100% current efficiency for production of cyclooctene oxide. At lower porphyrin concentrations, catalyst degradation occurs, and at low olefin concentrations, an apparent catalase-like side reaction lowers the yield of epoxide. The porphyrin degradation but not the catalase-like side reaction was lessened by using the protected porphyrins [Mn(TMP)Cl] and [Mn(T-F5PP)Cl]. © 1990, American Chemical Society. All rights reserved.