The Reactions of Electrogenerated [Ni(sacsac)₂]^-: Biomimetic Chemistry Related to Nickel Enzymes

Abstract

The electrochemical reduction of [Ni( sacsac )₂] ( sacsac = C₅H₇S₂- = pentane-2,4-dithionate) has been investigated by cyclic voltammetry and controlled-potential electrolysis in acetone/tetra- butylammonium tetrafluoroborate (0.1 M). The reactions of the reduction product(s) with CO, CO₂, CH₃I, C₁₂H₂₅SH, light and water have been surveyed. At a scan rate of 100 mV s-¹, [Ni( sacsac )₂] (0.5 mM ) undergoes a quasi-reversible one-electron reduction (∆ Ep = 88 mV) at -1.543 V (v. Fc+/0) and an irreversible four-electron oxidation at +0.635 V. The oxidation generates the 3,5-dimethyl-1,2-dithiolium cation, as evidenced by the observation of the (known) reduction of this cation at -0.840 V. The initial product of the reduction of [Ni( sacsac )₂] is a Lewis base, and reacts with light, water, CO, CO₂, CH₃I and C₁₂H₂₅SH. These reactions have been followed by electrochemical and spectroscopic methods. They appear to be biomimetic for a number of reactions observed for nickel enzymes.