Preparation and crystal structures of two phosphorus–sulphur rings: (PhP)3S3 and (PhP)2S4

Abstract

The 1 : 1 reaction between PPhCl₂ and (SnMe₃)₂S in CS₂ provides a convenient direct route to (PhP)₃S₃(1), which reacts with elemental sulphur to give (PhP)₂S₄(2). Both structures have been determined by X-ray diffraction using twinned crystals. Compound (1) is monoclinic, space group P2₁, with a= 8.884(2), b= 13.713(2), c= 8.309(2)Å, β= 106.61 (2)°, Z= 2, and R= 0.051 for 1 938 unique observed reflections. The structure contains an unsymmetrical five-membered ring with one exocyclic sulphur, and does not agree with a previous proposal based on n.m.r. data. Compound (2) is monoclinic, space group P2₁/c, with a= 6.624(1), b= 14.438(3), c= 7.667(2)Å, β= 95.31(2)°, Z= 2, and R= 0.060 for 880 unique observed reflections. The four-membered ring with two trans exocyclic sulphurs possesses a crystallographic centre of symmetry.