Reversible Apical Coordination of Imidazole between the Ni(III) and Ni(II) Oxidation States of a Dithiolate Complex: A Process Related to the Ni Superoxide Dismutase

A bisamine aliphatic dithiolate [NiIIN2S2] complex that does yield a metal-based oxidation has been synthesized. A square pyramidal [NiIIIN3S2]+ complex is generated by electrochemical oxidation in the presence of imidazole, mimicking the redox structural changes of NiSOD. In addition, EPR measurements coupled to DFT calculations demonstrate that the metal character in the redox active orbital increases drastically upon imidazole binding, implicating that these geometrical modifications are crucial for the stabilization of the NiIII state.