Zinc(II) thione and selone complexes: The effect of metal redox activity on ligand-based oxidation

Thione and selone ligands preferentially oxidize to protect redox active-metals from oxidation, but the effects of thione or selone coordination to a redox-inactive metal have not been examined. Therefore, Zn(II)-containing thione and selone complexes of the formulae Zn(L)(2)Cl-2 and [Zn(L)(4)](2+) (L = N,N'-dimethylimidazole thione, dmit, and selone, dmise) have been synthesized and their properties, including electronic spectra and DFT calculations, compared with analogous Fe(II) complexes. The Zn(dmit/dmise)(2)Cl-2 complexes were also oxidized with H2O2, resulting in oxidation and C=S/Se bond cleavage of the dmit and dmise ligands. Electrochemical studies show that upon redox-inactive Zn(II) coordination, dmit- and dmise-based oxidation potentials decrease relative to those of analogous redox-active Fe(II) complexes, demonstrating that the redox activity of the metal ion significantly effects the redox properties of the ligands.