Cathodic reductive couplings and hydrogenations of alkenes and alkynes catalyzed by the B₁₂ model complex

The reductive coupling and hydrogenation of alkenes were catalyzed by the B₁₂ model complex, heptamethyl cobyrinate perchlorate (1), in the presence of acid during electrolysis at −0.7 V vs. Ag/AgCl in acetonitrile. Conjugated alkenes showed a good reactivity during electrolysis to form reduced products. The product distributions were dependent on the substituents at the C[dbnd]C bond of the alkenes. ESR spin-trapping experiments using 5,5-dimethylpyrroline N-oxide (DMPO) revealed that the cobalt-hydrogen complex (Co–H complex) should be formed during the electrolysis and it functioned as an intermediate for the alkene reduction. The electrolysis was also applied to an alkyne, such as phenylacetylene, to form 2,3-diphenylbutane (racemic and meso) and ethylbenzene via styrene as reductive coupling and hydrogenated products, respectively.