Crystal and molecular structures of tungsten(VI) sulphide tetrachloride and tungsten(VI) sulphide tetrabromide

Abstract

Crystals of tungsten(VI) sulphide tetrachloride are triclinic, spacegroup P with Z= 2 in a unit cell of dimensions a= 8·278, b= 6·092, c= 6·923 Å, α= 85·96, β= 104·30, γ= 111·24°. Crystals of tungsten(VI) sulphide tetrabromide are monoclinic, spacegroup P2₁/c, with Z= 4 in a unit cell of dimensions a= 9·642, b= 6·024, c= 12·776 Å, β= 109·17°. The intensities of 844, for the former, and 530 reflections above background were collected by counter methods and refined to R 0·089 and 0·121 respectively. The molecular structures are very similar, each tungsten atom being strongly bonded to a sulphur atom (2·098, 2·079 Å) and to four halogen atoms (mean, W–Cl 2·28, W–Br 2·44 Å) in a square pyramidal arrangement with the sulphur atom at the apex. Each WSX₄ unit is associated with one other such unit through a weak W–X bond (3·049, 3·030 Å), which is trans to the W–S bond.