CsTb3STe4 und CsTb5S2Te6: Zwei pseudo-ternäre Caesium-Terbium-Chalkogenide mit geordneten S2−- und Te2−-Anionen

Abstract

Abstract By the oxidation of terbium metal with sulfur and tellurium in the presence of cesium bromide as flux at 850°C for 10 days, the first quaternary cesium terbium chalcogenides with ordered S2− and Te2− anions could be obtained as main products. The new compounds CsTb3STe4 and CsTb5S2Te6 occur as black needles. While CsTb3STe4 crystallizes in the orthorhombic space group Pnma with a=1924.08(16), b=433.61(3) and c=1493.47(13) pm for Z=4, CsTb5S2Te6 adopts the monoclinic space group C2/m with a=2146.17(18), b=431.42(3), c=1049.68(9) pm and β=102.064(3)° for Z=2. Both crystal structures are characterized by parallel cationic and anionic strands ( { [ STb 3 ] 7 + } ∞ 1 ${}_\infty ^1\{ {[{\rm{ST}}{{\rm{b}}_{\rm{3}}}]^{7 + }}\} $ and { [ CsTe 4 ] 7 − } ∞ 1 ${}_\infty ^1\{ {[{\rm{CsT}}{{\rm{e}}_4}]^{7 - }}\} $ for CsTb3STe4 as well as { [ S 2 Tb 5 ] 11 + } ∞ 1 ${}_\infty ^1\{ {[{{\rm{S}}_{\rm{2}}}{\rm{T}}{{\rm{b}}_{\rm{5}}}{\rm{]}}^{11 + }}\} $ and { [ CsTe 6 ] 11 – } ∞ 1 ${}_\infty ^1\{ {[{\rm{CsT}}{{\rm{e}}_6}]^{11-}}\} $ for CsTb5S2Te6), all running along [010]. The cationic chains result from vertex-connected [STb4]10+ tetrahedra (d(S2−–Tb3+)=271–277 pm), whereas face-sharing bicapped trigonal or square prisms [CsTe6+2]15− or [CsTe8+2]19−, respectively, form their anionic counterparts.