An electron spin resonance study of the reactions of oxidising radicals with dialkyl sulphides. Radical cations derived from anodic oxidation of R2S, (R2N)2S, and (R2N)2SO

Abstract

Constant current electrochemical oxidation of R₂S, (R₂N)₂S, and (R₂N)₂SO gives rise to radical cations which have been detected by e.s.r. spectroscopy. Dialkyl sulphides, except di-t-butyl sulphide which afforded the spectrum of Bu^t₂S⁺˙, gave the dimer cations (R₂SSR₂)⁺˙. Bis(dialkylamino) sulphides or sulphoxides gave monomer cations in which a large fraction of the spin density is on nitrogen. The g factors of (R₂SSR₂)⁺˙ increase with the bulk of R, and the g factors of both (R₂SSR₂)⁺˙ and Bu^t₂S⁺˙ are dependent on the temperature, the solvent, and the counteranion. The sulphide cation radicals have also been generated by photolysis of solutions containing R₂S, Bu^tOOBu^t, and CF₃CO₂H, and formation probably involves oxidation of the sulphide by Bu^tȮH. The neutral radical Bu^tO· and Me₃SiO· react with dialkyl sulphides by abstraction of hydrogen from an α-C–H group or by competing addition to sulphur to form a sulphuranyl radical. The e.s.r. spectra of the adducts R₂ṠOSiMe₃ have been detected and these radicals appear to be non-planar at sulphur with the unpaired electron probably confined to an S–O σ* orbital.