Electrochemical Behavior of Nickeladithiolene S,S-Dialkyl Adducts: Evidence for the Formation of a Metalladithiolene Radical by Electrochemical Redox Reactions

The electrochemical behavior of nickeladithiolene S,Sʹ-dialkyl adducts (alkyl = benzyl, methyl, tert-butyl) was investigated by using cyclic voltammetry (CV), visible, near-IR, and ESR spectroscopies and bulk electrolyses. The redox potentials of the S,Sʹ-dialkyl adducts were influenced by the electron -donating effect of the functional group on the sulfur atoms. The nickeladithiolene S,Sʹ-dibenzyl adduct [Ni{S(SCH2Ph)C2Ph2}2] (2) eliminated one benzyl radical by one-electron reduction, and then the monobenzyl adduct anion [Ni(S2C2Ph2){S2(CH2Ph)C2Ph2}]- (3-) was formed. Anion 3- was also formed by the reaction of nickeladithiolene dianion [Ni(S2C2Ph2)2]2- (12-) with 1 equiv of benzyl cation. When anion 3- was oxidized, the long-lived nickeladithiolene radical [Ni(S2C2Ph2){S2(CH2Ph)C2Ph2}] (3) was formed. The visible, near-IR, and ESR spectra of radical 3 could be measured and assigned. When radical 3 was further oxidized, the oxidant 3+ eliminated one benzyl cation, and then free nickeladithiolene (1) was generated.