Two-equivalent electrochemical reduction of a cyano-complex [Tl(CN)2] and the novel di-nuclear compound [(CN)5Pt−Tl]

Extending our recent insights in two-electron transfer microscopic mechanisms for a Tl^III/Tl^I redox system D.E. Khoshtariya, et al., Inorg. Chem. 41 (2002) 1728], the electrochemical response of glassy carbon electrode in acidified solutions of Tl^III (ClO₄)₃ containing different concentrations of sodium cyanide has been extensively studied for the first time by use of cyclic voltammetry and the CVSIM curve simulation PC program. The complex Tl^III(CN)₂]⁺ has been thoroughly identified electrochemically and shown to display a single well-defined reduction wave (which has no anodic counterpart), ascribed to the two-equivalent process yielding Tl^I(aq)]⁺. This behavior is similar to that of Tl^III(aq)]³⁺ ion in the absence of sodium cyanide, disclosed in the previous work, and is compatible with the quasi-simultaneous yet sequential two-electron transfer pattern (with two reduction waves merged in one), implying the rate-determining first electron transfer step (resulting in the formation of a covalently interacting di-thallium complex as a metastable intermediate), and the fast second electron transfer step. Some preliminary studies of the two-equivalent reduction of directly metal-metal bonded stable compound (CN)₅Pt^II-Tl^III]⁰ has been also performed displaying two reduction waves compatible with a true sequential pattern.