Nonaqueous Electrocatalytic Oxidation of the Alkylaromatic Ethylbenzene by a Surface Bound RuV(O) Catalyst

The catalyst [Ru(Mebimpy)(4,4′-((HO) 2 OPCH 2 ) 2 bpy(OH 2 )] 2+, where Mebimpy is 2,6-bis(1-methylbenzimidazol-2-yl)pyridine and 4,4′-((HO) 2 OPCH 2 ) 2 bpy is 4,4′-bis-methlylenephosphonato-2,2′-bipyridine, attached to nanocrystalline Sn(IV)-doped In 2 O 3 (nanoITO) electrodes (nanoITO|Ru II –OH 2 2+ ) has been utilized for the electrocatalytic oxidation of the alkylaromatics ethylbenzene, toluene, and cumene in propylene carbonate/water mixtures. Oxidative activation of the surface site to nanoITO|Ru V (O) 3+ is followed by hydrocarbon oxidation at the surface with a rate constant of 2.5 ± 0.2 M –1 s –1 ( I = 0.1 M LiClO 4, T = 23 ± 2 °C) for the oxidation of ethylbenzene. Electrocatalytic oxidation of ethylbenzene to acetophenone occurs with a faradic efficiency of 95%. H/D kinetic isotope effects determined for oxidation of ethylbenzene point to a mechanism involving oxygen atom insertion into a C–H bond of ethylbenzene followed by further 2e – /2H + oxidation to acetophenone.