Two-equivalent electrochemical reduction of a cyano-complex [TlIII(CN)2]+ and the novel di-nuclear compound [(CN)5PtII−TlIII]0

Extending our recent insights in two-electron transfer microscopic mechanisms for a TlIII/TlI redox system [D.E. Khoshtariya, et al., Inorg. Chem. 41 (2002) 1728], the electrochemical response of glassy carbon electrode in acidified solutions of TlIII (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 [TlIII(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 [TlI(aq)]+. This behavior is similar to that of [TlIII(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)5PtII–TlIII]0 has been also performed displaying two reduction waves compatible with a true sequential pattern.