Polysulfides in dimethylformamide: Only the radical anions S-3(-) and S-4(-) are reducible

The reduction mechanism of polysulfides in dimethylformamide (DMF) is examined. With this aim, Li2S6 + DMF solutions have been investigated by using cyclic voltammetry and time resolved spectroelectrochemical experiments coupling spectrophotometry and cyclic voltammetry. It is shown that the only reducible polysulfides in these solutions are S-3(-) and S-4(-). The experimental results are interpreted by the following mechanism: [GRAPHICS] This mechanism has been simulated and adjusted to the experimental voltammograms in a wide temperature (233 to 313 K) and scan rate (50 to 2000 mV/s) range. We discuss the experimental data, the choice of the mechanism and its ability to describe the experimental data. It is shown that this mechanism also describes the second reduction wave observed in solutions of sulfur (S-8) in DMF. (C) 1997 Elsevier Science S.A.