Stable cobalt(I) complexes of tetradehydrocorrins

Cyanation and nitration of cobalt(II) tetradehydrocorrin salts yield cobalt(III) derivatives which can be converted readily into crystalline neutral cobalt(I) complexes; these substituted cobalt(I) tetradehydrocorrins are reversibly oxidised to stable cobalt(II) complex at potentials anodic to the oxidation potential of the unsubstituted cobalt(I) complex.