Syntheses and Crystal Structures of Rb2B2Se7, Tl2B2Se7, Cs3B3Se10, and Tl3B3Se10: New Perseleno‐selenoborates with Polymeric Anionic Chains |
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Authors: | Arno Lindemann,Jö rn Kü per,Christoph Jansen,Joachim Kuchinke,Christian Kö ster,Adrienne Hammerschmidt,Matthias Dö ch,Timo Pruß ,Bernt Krebs |
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Abstract: | The perseleno‐selenoborates Rb2B2Se7 and Cs3B3Se10 were prepared from the metal selenides, amorphous boron and selenium, the thallium perseleno‐selenoborates Tl2B2Se7 and Tl3B3Se10 directly from the elements in evacuated carbon coated silica tubes by solid state reactions at temperatures between 920 K and 950 K. All structures were refined from single crystal X‐ray diffraction data. The isotypic perseleno‐selenoborates Rb2B2Se7 and Tl2B2Se7 crystallize in the monoclinic space group I 2/a (No. 15) with lattice parameters a = 12.414(3) Å, b = 7.314(2) Å, c = 14.092(3) Å, β = 107.30(3)°, and Z = 4 for Rb2B2Se7 and a = 11.878(2) Å, b = 7.091(2) Å, c = 13.998(3) Å, β = 108.37(3)° with Z = 4 for Tl2B2Se7. The isotypic perseleno‐selenoborates Cs3B3Se10 and Tl3B3Se10 crystallize in the triclinic space group P1 (Cs3B3Se10: a = 7.583(2) Å, b = 8.464(2) Å, c = 15.276(3) Å, α = 107.03(3)°, β = 89.29(3)°, γ = 101.19(3)°, Z = 2, (non‐conventional setting); Tl3B3Se10: a = 7.099(2) Å, b = 8.072(2) Å, c = 14.545(3) Å, α = 105.24(3)°, β = 95.82(3)°, γ = 92.79(3)°, and Z = 2). All crystal structures contain polymeric anionic chains of composition ([B2Se7]2–)n or ([B3Se10]3–)n formed by spirocyclically fused non‐planar five‐membered B2Se3 rings and six‐membered B2Se4 rings in a molar ratio of 1 : 1 or 2 : 1, respectively. All boron atoms have tetrahedral coordination with corner‐sharing BSe4 tetrahedra additionally connected via Se–Se bridges. The cations are situated between three polymeric anionic chains leading to a nine‐fold coordination of the rubidium and thallium cations by selenium in M2B2Se7 (M = Rb, Tl). Coordination numbers of Cs+ (Tl+) in Cs3B3Se10 (Tl3B3Se10) are 12(11) and 11(9). |
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Keywords: | Boron Selenium Selenoborates Solid‐state structures |
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