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Keywords:

  • Chalcogenide;
  • Uranium;
  • Thiophosphate;
  • Crystal structure;
  • Magnetic properties

Abstract

The new ternary compounds UP2S6, UP2S7, U(P2S6)2, and U3(PS4)4 were prepared from uranium metal, phosphorus pentasulfide, and sulfur at 700 °C. The crystal structures were determined by single-crystal X-ray diffraction methods. UP2S6 (I) crystallizes in the ZrP2S6 structure type [tetragonal, P42/m, a = 6.8058(7) Å, c = 9.7597(14) Å, Z = 2], which consists of central uranium(IV) atoms coordinated by P2S64– anions (staggered conformation). The anions are two-dimensional connectors for four uranium cations arranged in one plane. The structure of UP2S7 (II) [orthorhombic, Fddd, a = 8.9966(15) Å, b = 15.2869(2) Å, c = 30.3195(5) Å, Z = 16] is closely related to the monoclinic ZrP2S7 structure type. It consists of U4+ cations linked by P2S74– ligands, the resulting 3D network contains large pores (diameter approx. 3.5 × 16.7 Å). In the previously reported compound U(P2S6)2 (III) [I41/a, a = 12.8776(9) Å, c = 9.8367(10) Å, Z = 2], the metal atoms are coordinated by four bidentate P2S62– ligands. This arrangement can be considered as a pseudotetrahedral coordination of the uranium atoms by the linear ligands. Three of the resulting diamondoid frameworks are inseparably interwoven in order to optimize space filling. U3(PS4)4 (IV) [I41/acd, a = 10.7440(9) Å, c = 19.0969(2) Å, Z = 2] crystallizes in a defect variant of the PrPS4 structure type, with 50 % of the U2 sites statistically occupied with uranium atoms. The resulting stoichiometry is U3(PS4)4 with tetravalent uranium atoms. The structure of U3(PS4)4 consists of uranium atoms connected by PS43– groups, each PS4 group linking four central uranium atoms. Vibrational spectra, which were recorded for IIII, show good agreement between the obtained results and the expected values for the anionic units, while magnetic measurements confirm the presence of tetravalent uranium.