CYCLOVOLTAMMETRIC STUDIES ON THE DIMERIZATION OF METHYL ACRYLATE BY RUTHENIUM COMPLEXES

Electrochemical measurements are described on transition metal complex es which are or might be catalyst precursors for the tail-to-tail dime rization of methyl acrylate (MA). Thus, RuH2(PPh3)(4) and RuHCl(CO)(PP h3)(3) are studied electrochemically by cyclic voltammetry (CV) in var ious solvents including neat MA. It is shown that the activation of th e catalyst precursor RuH2(PPh3)(4) with trifluoromethanesulfonic acid and of RuHCl(CO)(PPh3)(3) with triethyloxonium tetrafluoroborate gener ates new complexes that are easy to reduce and rather difficult to oxi dize. The electrochemical measurements provide information on the deac tivation of the catalyst. CpRuH(PPH3)(2), which can easily be oxidized but can not be reduced, even at - 2.5 V versus SCE, does not act as a catalyst precursor neither in pure form nor in the presence of activa ting compounds. The ease of reduction or oxidation seems to be connect ed to a possible catalytic activity. It is, therefore, postulated that cyclic voltammetry can be a useful tool in the study of homogeneous t ransition metal catalysis. (C) 1998 Elsevier Science S.A. All rights r eserved.