Direct, indirect and assisted electrooxidation of benzenetricarbonylchromium derivatives. A comparative study in acetonitrile and in N,N-dimethylformamide

Abstract

The direct, indirect and assisted electrooxidations of benzenetricarbonylchromium (Bct) moieties were investigated in acetonitrile (MeCN) and at a glassy carbon anode. These results were compared with the results previously obtained in N,N-dimethylformamide (DMF). In the case of benzenetricarbonylchromium ( 1), the anodic oxidation was a 2-electron process in MeCN, with formation of a chromium(II) species, whereas three electrons were transferred in DMF where a chromium(III) species was generated. The indirect electrooxidation of 1 by catalysts was less efficient in MeCN than in DMF. Similarly, the assisted electrooxidation of the Bct moiety in molecules which contained both a Bct group and a redox system capable of serving as a catalyst, was less efficient in MeCN than in DMF. A ligand substitution in the intermediate Bct + cation by a molecule of solvent was suggested to occur in both catalytic and assisted oxidation processes. It would account for the lower efficiency in MeCN.