Reactions of tetraphosphorus trisulphide with organic disulphides under ultraviolet irradiation, and with sulphuryl chloride

Abstract

P₄S₃ under glass-filtered u.v. irradiation is rapidly cleaved by alkyl and aryl disulphides to give tetrathiophosphate esters, SP(SR)₃, and trithiophosphite esters, P(SR)₃(R = Me or Ph), in quantitative yield, as measured in the product mixture by ³¹P and ¹H n.m.r. spectroscopy. No sulphurisation of P₄S₃ was found. In a competition reaction, MeSSMe and PhSSPh reacted to a similar extent with P₄S₃ to give all eight possible products S_xP (SPh)_n(SMe)_{3 –n}(x= 0 or 1, n= 0–3) in relative quantities within each oxidation state approximating to a statistical distribution of ligands, but there was more MeS substitution of the phosphorus(V) products and more PhS substitution of the phosphorus(III) products. Reaction of MeSSPh with P₄S₃ gave similar results. Redistribution of ligands took place when a mixture of P(SMe)₃ and P(SPh)₃ was photolysed, and photolysis of a mixture of P(SMe)₃ and MeSSPh caused the PhS group to be distributed between the trithiophosphite and disulphide sites. P(SMe)₃ and P(SPh)₃ were not sulphurised by MeSSMe and PhSSPh respectively, but P(SMe)₃ was sulphurised to SP(SMe)₃ to a small extent by MeSSPh. P₄S₃ is similarly cleaved by sulphuryl chloride, but under thermal conditions, to give SPCl₃ and PCl₃, with no evidence for intermediates.