Electrocatalytic oxidation of styrene by a high valent ruthenium porphyrincation radical

A sterically-hindered carbonylruthenium(II) porphyrin Ru-II(CO)(TMP) (where TMP = meso-tetramesitylporphyrinato dianion) has been synthesized. Chemica l oxidation of Ru-II(CO)(TMP) by m-chloroperbenzoic acid (m-CPBA) gives the dioxoruthenium(VI) porphyrin (Ru-VI(O)(2)TMP). Cyclic voltammograms show t hat Ru-VI(O)(2)TMP is reversibly oxidized at E-1/2 = +1.24 V in CH2Cl2. Thi n-layer absorption spectra for oxidation of Ru-VI(O)(2)TMP at + 1.32 V indi cates that the product is a porphyrin cation radical (Ru-VI(O)(2)TMP+.). El ectrogenerated Ru-VI(O)(2)TMP+. reacts selectively with styrene to give phe nylacetaldehyde (96%) and benzaldehyde (4%). We report the first case of st yrene oxidation by high valent ruthenium porphyrin under electrochemical co nditions. An electrocatalytic oxidation reaction scheme is proposed. (C) 20 00 Elsevier Science S.A. All rights reserved.