Chemically Catalyzed Net Electrochemical Oxidation of Alcohols, Aldehydes, and Unsaturated Hydrocarbons Using the System (trpy)(bpy)Ru(OH2)2+/(trpy)(bpy)RuO2+

A mild electrocatalytic technique has been developed for the oxidation of selected alcohols, aldehydes, and unsaturated hydrocarbons at 25-50 °C using as catalysts the systems (bpy)2pyRu(0H2)2+/(bpy)2pyRu02+ and (trpy)(bpy)-Ru(0H2)2+/(trpy)(bpy)Ru02+. The organic compounds were dissolved or dispersed in an aqueous buffer solution of the catalyst, and the net oxidations were carried out using conventional three-electrode electrolysis cells at applied potentials which were sufficient to cause the oxidation of Ru(II) to Ru(IV) (0.6-0.8 V vs. SCE). Background currents in the absence of catalyst were negligible. Using the electrocatalytic approach, 2-propanol and ethanol were oxidized to acetone and acetate, respectively, and acetaldehyde was oxidized to acetate. Toluene was oxidized to benzoate anion, p-xylene to terephthalate dianion, and p-phthalate anion to terephthalate quantitatively, in all three cases without the appearance of intermediates. Ethylene is unreactive, but cyclohexene was oxidized first to 2-cyclohexen-l-one and then to p-benzoquinone, which decomposes in solution. The (trpy)(bpy)Ru(0H2)2+ catalyst is greater than 75% recoverable after 100 catalytic cycles.