ELECTROCHEMICAL CARBONYLATION OF ORGANOIRON METHYL COMPLEX - A STUDY OF REACTION INTERMEDIATES

The one-electron reduction of CpFe(CO)(2)CH3 has been investigated by voltammetry and Fourier transform IR spectroelectrochemistry. The redu ction initiates the insertion of CO ligand in the Fe-CH3 bond. The dis sociation of a CO group proceeds in a parallel reaction. Reaction inte rmediates, the acyl derivative and released CO, form the radical anion of a complex CpFe(CO)(2)(COCH3) which is able to reduce the parent co mpound. The reversible redox potential -1.8 V of CpFe(CO)(2)(COCH3) al lows the regeneration of its radical anion which drives a catalytic cy cle. The lifetime of intermediates is shortened by side reactions, one of which is the migration of the acyl group from the central atom to the cyclopentadienyl ring. This explains the apparent discrepancy betw een products observed in preparative scale electrolysis and the absenc e of catalytic effects in routine voltammetric experiments.