ELECTROCHEMICAL STUDIES OF NICKEL AND PLATINUM COMPLEXES OF 5,6-DIHYDRO-1,4-DITHIIN-2,3-DITHIOLATE - THE FORMATION MECHANISM OF DERIVED [M(DDDT)2]3(BF4)2 CONDUCTING COMPOUNDS

Cyclic and linear voltammetric studies of the redox behavior of (R4N)[ M(dddt)2] complexes (dddt2- = 5,6-dihydro-1,4-dithiin-2,3-dithiolato; M = Ni, R = Et; M = Pt, R = Bu), using standard millimetric electrodes at low potential scan rates, are reported. Analysis of these data, to gether with the ESR characterization of the products resulting from th e redox reactions involved, confirm that the (R4N)[M(dddt)2] complexes are reversibly reduced (E1/2 almost-equal-to -0.7 V vs. Ag/AgCl) and oxidized (E1/2 almost-equal-to 0.0 V vs. Ag/AgCl) to the corresponding divalent (R4N)2[M(dddt)2] complexes and the neutral M(dddt)2 complexe s, respectively. At a high anodic potential (almost-equal-to 0.9 V vs. Ag/AgCl), an additional, irreversible (or quasi-reversible) oxidation wave is observed in the cyclic voltamperogram of the nickel (or the p latinum) compound. This wave is associated with the formation of [M(dd dt)2]3(BF4)2 partially oxidized conductive compounds. The mechanism of this reaction is studied under non-stationary conditions by cyclic vo ltammetry using ultra-microelectrodes at high potential scan rates. It is shown that the high anodic potential oxidation process involves a one-electron electrochemical transfer, leading to the [M(dddt)2]+ spec ies, followed by chemical reaction between the [M(dddt)2]+ species and the neutral M(dddt)2 species, leading to the {[M(dddt)2]3}2+ species.