Studies on Cobaloxime Compounds. IV. The Polarography of Cobaloximes

Abstract Various types of cobaloximes, e.g., Co-alkyl derivatives with different bases as an axial ligand and polymeric cobaloximes with the general formula of Co(OH)(DH)2(Copoly—AM-VPy) (DH: dimethylglyoximato monoanion) in which Copoly—AM-VPy is a low-molecular-weight copolymer of acrylamide and 4-vinylpyridine, were prepared, and their half-wave potentials in cathodic reduction were compared to each other and to those of a few vitamin B12 compounds. All of them showed a single irreversible cathodic wave. Methyl- and cyano-cobaloximes were reduced at more negative potentials than the corresponding methylcobalamin and cyanocobal-amin(vitamin B12). The half-wave potential of methylcobaloxime shifted in the direction of the more negative potentials as the donating strength of the axial base increased. This was correlated with the charge-transfer transition energies of those cobaloximes as determined from their electronic spectra. The polymeric cobaloximes were reduced at less negative potentials than the others.