Reactivity of X3P Compounds with Elemental Sulfur, Carbon Disulfide or Both, to Yield X3PS, X3P.CS2 or X3P.Sn.CS2 Adducts

Abstract

Kinetic constants k2 have been obtained for the reaction of sulfur with 25 PIII compounds in toluene or hexane. In the series PhnMe3-nP (n = 1−3) or PhnBu3-nP (n = 0−3), log k2 decreases linearly with ∑χi(χi=Tolman's electronic parameter of each ligand on P), taken as a gauge for the donor strength of P. Dramatic deviations from additivity are observed for the series PhnP(OEt)3-n, PhnP(OPh)3-n and BunP(OEt)3-n(n = 0–3); the deviation is smaller for PhnPCl3-n and even smaller for PhnP(NEt2)3-n. The results are discussed in terms of P-coordination (PIV vs. PV), stability and geometry of the intermediate X3P.S8 or of the transition state leading to this adduct, emphasis being laid on the donor/acceptor character of the P site. A similar dependence on X governs the reactivity of X3P with S8, CS2 or both, to give X3PS, X3P.CS2 (binary red adduct) or X3P.Sn.CS2 (ternary yellow adduct) respectively; an explanation for this parallelism is proposed.