Preparation and crystal structures of two phosphorus–sulphur rings: (RPS)₄and (RPS₂)₂(R = C₆H₂Me₃-2,4,6)

The 1:1 reaction between PRCl2(R = C6H2Me3-2,4,6) and (Me3Si)2S in toluene yields (RPS)4(1) which slowly disproportionates under mild conditions (35–40 °C, 3 d) to (RPS2)2(2). Both structures have been determined by X-ray diffraction. Compound (1) is monoclinic, space group Cc, with a= 2 299.3(7), b= 1 167.9(3), c= 1 937.8(6) pm, β= 130.65(2)°, and Z= 4; R= 0.050 for 3 209 unique observed reflections. The eight-membered (PS)4 ring adopts the crown conformation but is disordered. Compound (2) is monoclinic, space group P21/c, with a= 890.1 (2), b= 1 845.2(12), c= 641.3(1) pm, β= 98.74(1)°, and Z= 2; R= 0.062 for 904 unique observed reflections. The four-membered ring with two trans exocyclic sulphurs possesses a crystallographic centre of symmetry.