Dithiocarbamates of Nickel in the Formal Oxidation States I-IV. Electrochemical Study

Abstract

The electron-transfer properties of 16 nickel(II) dithiocarbamate complexes have been studied in acetone at a platinum electrode. Their oxidation (+0.8 to +1.0 V) is difficult and irreversible with the overall process conforming to the stoichiometry 3Ni(R2dtc)2⟶ 2[Ni(R2dtc)3]++ Ni2++ 4e–. The nickel(IV) cation exhibits two successive, relatively facile, reversible reduction steps corresponding to the one-electron-transfer series [formula omitted]. Both reduction products are unstable according to the equilibria [formula omitted]. Although the formally nickel(III) species could not be prepared and isolated chemically, they are readily formed from Ni(R2dtc)2 and the electrochemically generated R2NCSS· radical. The Ni(R2dtc)2 complexes undergo a one-electron reduction at quite negative potentials (-1.2 to -1.5 V): Ni(R2dtc)2+ e-≨ [Ni(R2dtc)2]-. Substituent effects on the redox potentials of nickel dithiocarbamates parallel closely those measured for the oxidation of the free ligand: [R2dtc]-⟶ R2NCSS· + e-. Mixed-ligand species have been characterized by voltammetry and unusual reactions of some of the complexes are reported. © 1975, American Chemical Society. All rights reserved.