Reactions of organosulphur ligands on tungsten centres. Evidence for carbonium ion formation in the degradation of alkanethiolatopentachlorotungsten(VI) species
Abstract
The monothiolate derivatives of tungsten(VI) chloride, [WCl5(SR)](R = Me, Et, cyclohexyl, But, But, CH2,Ph, or Ph), have been found to be unstable with respect to at least two modes of degradation. Heterolytic cleavage of the carbon–sulphur bond to generate a carbonium ion, which can further abstract chloride to give WSCl4+ RCl, is the preferred pathway if the R+ ion is relatively stable. The intermolecular elimination of R2S2 is the alternative route for degradation and is the exclusive one for R = Ph, where the carbonium ion is very unstable. The only pure [WCl5(SR)] compounds which have been isolated are [WCl5(SMe)] and [WCl5(SPh)] and even these slowly decompose at room temperature over a period of a few weeks.