Cleavage of Cobalt-Alkyl Bonds of N-Dialkyleobalt (III) Complexes with Organic Oxidants Catalyzed by Mg(CIO₄)₂ and HCIO₄

Electron transfer from crs-dialkylcobalt (III) complexes, cis-[R₂Co(bpy)₂]C1O₄ (R=Me, Et; bpy=2, 2'-bipyridine), to strong organic oxidants (2, 3-dichloro-5, 6-dicyano-p-benzoquinone, 2, 3-dieyano-p-benzoquinone, tetracyanoethylene, and 7, 7, 8, 8-tetraeyano-p-quinodimethan) in aeetonitrile results in the cleavage of a pair of the cobalt-alkyl bonds to yield the coupled products (R-R) exclusively. The cleavage of the cobalt-alkyl bonds of cis-[R₂Co(bpy)₂]⁺ with weaker organic oxidants such as p-benzoquinone was catalyzed significantly by Mg(C1O₄)₂ and HC1O₄. The presence of both Mg(C1O₄)2 and HC1O₄ showed a much larger catalytic effect than that of Mg(C1O₄)₂ or HC1O₄ alone. It has been studied a correlation of the logarithm of rate constants with the difference of the redox potentials between cis-[R₂Co(bpy)₂]⁺ and the oxidants in the absence and presence of Mg(C1O₄)₂, and presence of both Mg(C1O₄)₂ and HC1O₄. Then, the role of Mg(C1O₄)₂ and HC1O₄ in the cleavage of the cobalt-alkyl bonds of cis-[R₂Co(bpy)₂]⁺ with p-benzoquinone derivatives was found to be due to the increased electron-accepting property of the oxidants, resulting in the acceleration of electron transfer from cis-[R₂Co(bpy)₂]⁺ to the oxidants.