Cobalt(III) Complexes of Dimethylglyoxime with No Direct Cobalt–Carbon Bond as Possible Non‐Organometallic Models for Vitamin B12

Abstract

Abstract Cobaloximes of the type [CoX(Hdmg)2B] [X = Cl, CN, SCN or I, and B = py (pyridine), 4‐aminopy (4‐aminopyridine), or bipy (2,2′‐bipyridine)], [CoCl2(Hdmg)B] [B = bipy and phen (1,10‐phenathroline)], and [CoPF4(Hdmg)2py] were synthesized and characterized by elemental analyses, melting points, solubility, conductivity, room temperature, magnetic susceptibility measurements, infrared and UV‐VIS electronic spectra, and cyclic voltammetry. The complexes melted/decomposed at 220–314 °C and, with the exception of a few, many of them dissolved only in coordinating organic solvents. The complexes are orange to brown. They are also non‐electrolytes in organic solvents. The IR spectra indicated that the complexes coordinate through the N atom of the oxime group of each ligand. The magnetic susceptibilities and electronic spectra of the complexes indicated that they are low‐spin d6 octahedral. Electrochemical studies on some of the complexes, using cyclic voltammetry, revealed that some of the complexes underwent reversible oxidation–reduction and are, therefore, viable models for vitamin B12. A variety of structures have been proposed for the complexes.