ELECTROCATALYTIC DIOXYGEN REDUCTION IN THE PRESENCE OF A RHODOXIME

Polarographic and voltammetric evidences are reported for the producti on of intermediates superoxo [Rh]OO and hydroperoxo [Rh]OOH derivative s at the electrode surface, in the reduction of dioxygen in the presen ce of rhodium bis(dimethylglyoximato) chloro triphenylphosphine, [CIRh (III)(DMG)(2)(PPh3)] (I), in the absence and in the presence of proton s in non-aqueous solvents. In the latter case the electrocatalytic red uction of dioxygen is observed. From the trends of the concentrations of dioxygen vs the rhodium complexes, a mechanism for the electrochemi cal process is proposed. The molar ratio of dioxygen to the rhodium co mplex when the latter is completely consumed for the formation of the adduct, as compared with the 1:1 stoichiometric ratio determined by th e Hill plot, together with the influence of the electrode material, su ggests that the reduction of dioxygen involves adsorbed species. (C) 1 998 Elsevier Science S.A. All rights reserved.