Cyclic voltammetric and spectrophotometric investigation of the catalytic reduction of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) by electrogenerated cobalt(I) salen in dimethylformamide saturated with carbon dioxide

Abstract

A comparative study of the cobalt(I) salen-catalyzed electrochemical reduction of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) in both carbon dioxide- and argon-saturated dimethylformamide (DMF) containing tetra-n-butylammonium tetrafluoroborate (TBABF4) has been carried out by means of cyclic voltammetry with a glassy carbon electrode. Catalytic reduction of CFC-113 by cobalt(I) salen appears to be more efficient in a carbon dioxide-saturated medium. Chlorotrifluoroethene (a degradation product of CFC-113) is also more efficiently reduced by electrogenerated cobalt(I) salen in the presence of carbon dioxide. No evidence for the cobalt(I) salen-catalyzed reduction of trifluoroethene (another degradation product of CFC-113) has been seen. Preliminary bulk electrolyses of cobalt(II) salen–CFC-113 mixtures in a carbon dioxide-saturated medium have indicated the formation of chlorotrifluoroethene, trifluoroethene, and 1,1,1,2-tetrafluoroethane. However, these three compounds do not account for all of the original CFC-113; therefore, future work will focus on the possible production of 3,3-dichloro-2,2,3-trifluoropropanoic acid and 2,3,3-trifluoroacrylic acid that might arise via carboxylation of anionic intermediates derived from the reduction of CFC-113. Furthermore, ultraviolet–visible spectrophotometry has confirmed that cobalt(I) salen and carbon dioxide interact to preserve the fidelity of the catalyst.