The crystal structure of Tl 2[Ge 2S 4], a ternary thallium(I) sulphide with divalent and tetravalent germanium

Abstract

The crystal structure of Tl 2[Ge 2S 4] was determined from single-crystal X-ray data measured on a four-circle diffractometer. The compound is orthorhombic (space group, Pmnb) with a = 6.633(2) A ̊ , b = 8.824(2) A ̊ , c = 13.977(4) A ̊ and Z = 4. The structure is characterized by infinite double chains ∞ 1[Ge 2 IIGe 2 IVS 8] 4− parallel to [100] which are held together by Tl + cations situated between them. The double chains are composed of single chains containing alternately divalent and tetravalent germanium atoms linked by sulphur atoms. These single chains are linked in pairs by sulphur bridges between the germanium(II) and germanium(IV) atoms. The divalent germanium atoms are each bonded to three sulphur atoms, thus forming ψ-tetrahedral GeS 3 arrangements (mean Ge-S distance, 2.355 Å). The tetravalent germanium atoms are tetrahedrally coordinated to four sulphur atoms (mean Ge-S distance, 2.224 Å). The nine sulphur atoms around Tl(2) form a distorted tricapped trigonal prism. The same configuration is adopted by eight sulphur atoms and one germanium(II) atom around Tl(1). The mean Tl-S distance is 3.437 Å and the Tl-Ge II distance is 3.133 Å, with the lone pair of electrons directed towards the thallium atom.