Fluorination of dimethyl sulphide. Formation of the fluorodimethylsulphonium cation, [Me2SF]+, and dimethylsulphur difluoride, Me2SF2

Abstract

The controlled reaction of dimethyl sulphide with xenon difluoride in a non-acidic medium gives rise via CH₂FSMe to a product best formulated as [Me₂SCH₂SMe]⁺[F(HF)_n]^–. In HF solution at –23 °C, however, the reaction affords the fluorodimethylsulphonium cation, [Me₂SF]⁺, solid derivatives of which have also been prepared by the reaction of XeF₂ with Me₂S·A (A = BF₃ or AsF₅); the species have been characterised by their ¹H and ¹⁹F n.m.r. and vibrational spectra. With CDCl₃ as a diluent, Me₂S reacts with an excess of AgF₂ at –23 °C to provide the first evidence of the thermally unstable dimethylsulphur difluoride, Me₂SF₂. The ¹H and ¹⁹F n.m.r. spectra have served to characterise the new compound and to chart its decomposition (to CH₂FSMe) and other reactions.