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Die Serie caesiumhaltiger Thioarsenate(V) der Lanthanoide vom Formeltyp Cs3 Ln[AsS4]2 mit Ln = La–Nd und Sm
Zeitschrift für Naturforschung B ( IF 0.8 ) Pub Date : 2024-01-12 , DOI: 10.1515/znb-2023-0066 Katja Engel 1 , Thomas Schleid 1
Zeitschrift für Naturforschung B ( IF 0.8 ) Pub Date : 2024-01-12 , DOI: 10.1515/znb-2023-0066 Katja Engel 1 , Thomas Schleid 1
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Cesium-containing thioarsenates(V) of lanthanoids with the composition Cs3 Ln [AsS4 ]2 can be prepared for Ln = La–Nd and Sm by the oxidation of the lanthanoid metals in the presence of orpiment (As2 S3 ), cesium sesquisulfide (Cs2 S3 ) and elemental sulfur (S). The reaction mixtures were handled under argon atmosphere and heated in fused silica ampoules to a moderate reaction temperature of 500 °C. Single crystals of this Cs3 Ln [AsS4 ]2 series appear as yellowish, transparent rods that are not stable to moist air and water. Their monoclinic crystal structure was determined from single-crystal X-ray diffraction data. The cesium-containing thioarsenates(V) Cs3 Ln [AsS4 ]2 with Ln = La–Nd and Sm crystallize isotypically with Rb3 Sm[PS4 ]2 in the non-centrosymmetric monoclinic space group P 21 with Z = 2. The lattice parameters range between a = 997–1015 pm, b = 699–703 pm, c = 1192–1195 pm and β = 90.2–90.4°. There are two crystallographically different As5+ cations and one unique Ln 3+ cation present, all coordinated by sulfur anions. Tetrahedral [AsS4 ]3− anions form two functionally different units working either as bridging units between three Ln 3+ cations or as terminal ligands for Ln 3+ . [Ln S8 ]13− polyhedra form ∞ 1 { [ Ln S 2 / 2 v S 6 / 1 t ] 11 − } ${}_{\infty }^{1}\left\{{[\mathit{Ln}{\mathrm{S}}_{2/2}^{\mathrm{v}}{\mathrm{S}}_{6/1}^{\mathrm{t}}]}^{11-}\right\}$ chains propagating along [010], which are separated by Cs+ cations with coordination numbers as high as C.N. = 9, 10 and 11. Surprisingly, the eighth interatomic distance d (Ln –S3) does not follow the lanthanoid contraction, but increases with decreasing ionic radius, changing the coordination polyhedron of Ln 3+ from a bicapped to a monocapped trigonal prism upon the transition from Nd to Sm, and causing a structural break in the crystal structure of this series. The results of Raman spectroscopic measurements on single crystals of Cs3 La[AsS4 ]2 have confirmed the presence of [AsS4 ]3− tetrahedra as structural building blocks.
更新日期：2024-01-12
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