HALOGEN-FACILITATED PREPARATION OF S4(ASF6)2.XSO2(X-LESS-THAN-OR-EQUAL-TO-1) AND S4(SB2F11)2, AND A CONVENIENT SYNTHESIS OF SE4(ASF6)2 AND SE4(SB2F11)2

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 less-than-or-equal-to 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 M4(2+), an unidentified Sb(v) fluoronion 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.