Stabilization of sulfenyl(poly)selenide ions in N,N-dimethylacetamide

Abstract

Whereas redox processes resulted from the reactions PhSe⁻/S₈ or PhSe₂Ph/S₃˙⁻, mixed anions RSSe_y⁻ (R = Ph, PhCH₂; y = 1–3) were obtained by the slow addition of solid selenium to thiolate ions in N,N-dimethylacetamide. The RS⁻ + n Se reactions, which were investigated by spectroelectrochemistry, led initially (n = 1) only to the formation of RSSe⁻ ions. These species oxidized into RS₂R faster than RS⁻ on a gold electrode, with the simultaneous electrodeposition of very reactive microcrystals of selenium. On a preparative scale, the substitution of RSSe⁻ ions (R = CH₃, Ph) on alkyl halides yielded RSSeR′ compounds (R′ = PhCH₂, CH₃, respectively) which greatly disproportionated. Further additions of Se (n = 2, 3) to RS⁻ ions led to RSSe₂⁻ and RSSe₃⁻ in equilibrium with RS₂R and mixtures of Se_x²⁻ polyselenide ions (x = 4,6; 6,8). Visible spectra of RSSe₂⁻ and RSSe₃⁻ ions were calculated from the study of the backward reactions RS₂R + Se_x²⁻ (x = 4, 6).