Halogen-facilitated preparation of S4(AsF6)2·xSO2(x⩽ 1) and S4(Sb2F11)2, and a convenient synthesis of Se4(AsF6)2 and Se4(Sb2F11)2

Abstract

Sulfur reacted with an excess of AsF₅ at room temperature in the presence of a trace amount of halogen (X₂= Cl₂, Br₂ or I₂) or AsCl₄AsF₆ in SO₂ to give S₄(AsF₆)₂·xSO₂(x⩽ 1) quantitatively in a few minutes. A similar, but slower, reaction with SbF₅ in SO₂ or AsF₃ at room temperature gave quantitative yields of S₄(Sb₂F₁₁)₂. The vibrational spectra of these salts with tentative assignments are reported. The corresponding preparations of Se₄(AsF₆)₂ and Se₄(Sb₂F₁₁)₂ are also greatly facilitated by the presence of traces of halogen. Reactions of sulfur (or selenium) with SbF₅ with and without traces of X₂ in SO₂ designed to give M₄(SbF₆)₂(M = S or Se) gave products that contained M₄²⁺, an unidentified Sb^V fluoroanion and some Sb^III-containing species. A comparative study was made on the effect of solvent, oxidising agent and facilitating reagent on the course of reaction. Possible reaction pathways for oxidation of sulfur (or selenium) by AsF₅(or SbF₅) with and without the addition of traces of X₂ or AsCl₄AsF₆ have been proposed.