Electrochemical and chemical oxidation of S 2 COEt Ϫ , Ni(S 2 COEt) 2 , and [Ni(S 2 COEt) 3 ] Ϫ have been studied by CV and in situ UV-VIS spectroscopy in acetonitrile. Cyclic voltammograms of S 2 COEt Ϫ and Ni(S 2 COEt) 2 display one (0.00 V) and two (0.35 and 0.80 V) irreversible oxidation peaks, respectively, referenced to an Ag/Ag ϩ (0.10 M) electrode. However, the cyclic voltammogram of [Ni(S 2 COEt) 3 ] Ϫ displays one reversible (Ϫ0.15 V) and two irreversible (0.35, 0.80 V) oxidation

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... , referenced to an Ag/Ag ϩ electrode. The low temperature EPR spectrum of the oxidatively electrolyzed solution of (NEt 4 )[Ni(S 2 COEt) 3 ] indicates the presence of [Ni III (S 2 COEt) 3 ], which disproportionates to Ni(S 2 COEt) 2 , and the dimer of the oxidized ethylxanthate ligand, (S 2 COEt) 2 ((S 2 COEt) 2 = C 2 H 5 OC(S)SS(S)COC 2 H 5 ), with a second order rate law. The final products of constant potential electrolysis at the first oxidation peak potentials of S 2 COEt Ϫ , Ni(S 2 COEt) 2 , and [Ni(S 2 COEt) 3 ] Ϫ are (S 2 COEt) 2 ; Ni 2ϩ (sol) and (S 2 COEt) 2 ; and Ni(S 2 COEt) 2 and (S 2 COEt) 2 , respectively. The chemical oxidation of S 2 COEt Ϫ to (S 2 COEt) 2 , and [Ni(S 2 COEt) 3 ] Ϫ to (S 2 COEt) 2 and Ni(S 2 COEt) 2 were also achieved with iodine. The oxidized ligand in the dimer form can be reduced to S 2 COEt Ϫ with CN Ϫ in solution.