Electrochemical generation of 17-electron cation radicals from arene-M(CO)3 (M = Cr, Mo, W) and thiophene-Cr(CO)3 complexes in MeCN: Conventional cyclic voltammetric studies with digital simulation and microelectrode voltammetry in the absence of supporting electrolyte

Article abstract of DOI:10.1016/0022-328X(92)83116-Y

One-electron electrochemical oxidation of arene-M(CO)3 (M = Cr, Mo, W) and thiophene-M(CO)3 complexes in acetonitrile produces 17-electron cations (MeCN)nM(CO)6-n⁺.Thus oxidation of LCr(CO)3, (L = C6H6, PhCl, PhNMe2, thiophene, 3-methylthiophene) in acetonitrile leads to a rapid follow-up reaction in which the intermediate (MeCN)3Cr(CO)3⁺ is detected by cyclic voltammetry.Oxidations in MeCN are not affected by redox catalysis, confirming a simple substitution mechanism.Increasing the concentration of the complex has no effect on the yield of MeCN substituted product, again ruling out bimolecular decomposition pathways.The reaction is very rapid and quite distinct from photochemical or thermal substitution of these complexes.Microelectrode steady-state voltammetry shows that all the arene complexes undergo two successive one-electron transfers in MeCN.Reproducible microelectrode voltammograms could only be obtained in MeCN in the absence of supporting electrolyte; addition of supporting electrolyte rapidly diminished the electrode response owing to electrode coating.