SULFURISATION OF AMINO TETRAPHOSPHORUS TRICHALCOGENIDE COMPOUNDS

Amino tetraphosphorus trisulfides alpha-P4S3(NR(1)R(2))(2) reacted wit h S-8 under photolysis using visible light, in moderate or low convers ion, to give alpha-P4S2(S)(NR(1)R(2))(2), in which the added sulfur at om was exocyclic. For NR(1)R(2) = NPr2i, three isomers were found: a p air of diastereomers corresponding to attachment of the sulfur atom to a nitrogen-carrying phosphorus atom either with retention or with inv ersion of its configuration, and an isomer containing a sulfurised bri dgehead phosphorus atom. For NR(1)R(2) = NMePh, only the two diastereo mers were seen. Photolysis of a mixture of alpha-P4Se3(NMePh)(2) and a lpha-P4Se3(NMePh)I with S-8 gave as major products alpha-P4SSe2(NMePh) (2) and alpha-P4SSe2(NMePh)I, in which sulfur had replaced the bridgin g selenium atom in the starting compounds. This provides a synthesis o f compounds alpha-P(4)SSe(2)XY in which sulfur occupies a specific ske letal position, rather than being randomly distributed. All products w ere characterised by P-31 NMR in unseparated solutions. Ab initio MO c alculations of geometry and of CIAO NMR chemical shifts at the 3-21G level for three isomers of the unknown model compound alpha-P4S3(S)(NH 2)(2), and two isomers of alpha-P4S3(NH2)(2), allowed identification o f the observed isomer of alpha-P4S3(S)(NPr2i)(2) with a sulfurised bri dgehead, but relative assignment of the two diastereomers to their NMR parameters remains a hypothesis.