Catalytic Reduction of 4,4[sup ʹ]-(2,2,2-Trichloroethane-1,1-diyl)bis(chlorobenzene) with Cobalt(I) Salen Electrogenerated at Vitreous Carbon Cathodes in Dimethylformamide

Cyclic voltammetry (CV) and controlled-potential electrolysis have been utilized to investigate the catalytic reduction of 4,4'-(2,2,2-trichloroethane-1,1-diyl)bis(chlorobenzene) (DOT) by cobalt(I) salen electrochemically generated at a carbon cathode in dimethylformamide containing 0.050 M tetramethylammonium tetrafiuoroborate. As a prelude to this study, CV has revealed that direct reduction of DDT at a glassy carbon disk electrode shows six peaks; the process associated with each peak has been assigned on the basis of an examination of the electrochemistry of various reduced forms of DDT. CVs for the reduction of cobalt(H) salen in the presence of DDT exhibit the classic characteristics of a catalytic process, including an enhanced cathodic current for the cobalt(II) salen-cobalt(I) salen redox couple and a disappearance of the anodic peak for oxidation of cobalt(I) salen. Bulk electrolysis of solutions containing cobalt(II) salen and DDT at a reticulated vitreous carbon cathode results in the formation of a mixture of products-4,4'-(2-chloroethene-1,1-diyl)bis(chlorobenzene), 4,4'-(ethene-1,1-diyl)bis(chlorobenzene) (DDNU), 1-chloro-4-(2-chloro-1-phenylvinyl)benzene (an isomer of DDNU), 4,4'-(2,2-dichloroethene-1,1-diyl)bis(chlorobenzene), and 4,4'-(2,2-dichloroethane-1,1-diyl)bis(chlorobenzene). A mechanistic scheme is proposed to account for the formation of products.