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  • 1
    ISSN: 0044-2313
    Keywords: Tetrapotassium biphosphidoberyllate, -biarsenidoberyllate, -biantimonidoberyllate ; crystal structure ; vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: K4BeP2, K4BeAs2, and K4BeSb2 Compounds with Linear [BeX2]4- Anions (X = P, As, Sb)The title compounds are synthesized from the elements. K4BeP2 and K4BeAs2 are isostructural and crystallize trigonal rhombohedrally in the space group R3m (No. 166) with Z = 3. The partial structure of the potassium atoms corresponds to a closest packing of rotational ellipsoides, which envelope an elongated K14-polyhedron (combination of rhombohedron and hexagonal prism). The polyhedrons are filled with linear [BeX2]4- anions, which are the analoga to BeCl2 molecules. The bond lengths are: d(Be—P) = 198.2 pm and d(Be—As) = 206.0 pm. IR spectra confirm the presence of [Sb—Be—Sb]4- anionic groups in K4BeSb2, which crystallizes in the hexagonal system with Z = 2. The vibrational spectra of the compounds are measured. The assignment of the observed frequencies is based on the D∞h symmetry of an isolated [X—Be—X]4- unit.
    Notes: Die Titelverbindungen wurden aus den Elementen dargestellt. K4BeP2 und K4BeAs2 sind isotyp und kristallisieren trigonal-rhomboedrisch in der Raumgruppe R3m (Nr. 166) mit Z = 3. Die Teilstruktur der Kaliumatome entspricht einer dichtesten Packung von Rotationsellipsoiden, welche ein gestrecktes K14-Polyeder (Kombination von Rhomboeder und hexagonalem Prisma) einhüllen. Die Polyeder sind durch lineare [BeX2]4--Anionen aufgefüllt, Analoga des BeCl2-Moleküls. Die Bindungslängen sind d(Be—P) = 198,2 qm und d(Be—As) = 206,0 pm. IR-Spektren belegen die Existenz von [Sb—Be—Sb]4--Anionen auch in K4BeSb2, welches im hexagonalen System mit Z = 2 kristallisiert. Die Schwingungsspektren der Verbindungen wurden gemessen. Die Zuordnung der beobachteten Frequenzen basiert auf der D∞h-Symmetrie einer isolierten [X—Be—X]4--Einheit.
    Additional Material: 3 Ill.
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  • 2
    ISSN: 0044-2313
    Keywords: Antimonide triantimonidometallates(III) ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Antimonide Triantimonidometallates(III) Cs6K3Sb[AlSb3] and Cs6K3Sb[GaSb3]The novel compounds Cs6K3Sb[AlSb3] and Cs6K3Sb[GaSb3] are formed from stoichiometric mixtures of Cs, AlSb (GaSb) and KSb in sealed niobium ampoules at 950 K. The hexagonal structures are especially characterized by one-dimensional rod packings 1∞[Cs6K3Sb] which are formed from columns of condensed (Cs6K6/2) icosahedra. The icosahedra are centered by Sb3-- anions. The trigonal planar anions [AlSb3]6-- and [GaSb3]6-- are embedded between the icosahedra columns, and they are coordinated by alkali metal atoms. The FIR spectra were assigned to the vibrations of the [MSb3]6-- anions, with respect to the 6m2-D3h symmetry.(P63/mmc, No. 194; a = 1101.7 and 1097.2 pm; c = 1158.9 and 1150.1 pm; Z = 2; Single crystal data: 574 and 546 reflections; R = 0.073 and 0.029. Distances:d(Al—Sb) = 265.4 pm; d(Ga—Sb) = 265.1 pm; d(Sb—Cs) = 401.6-423.0 pm; d(Sb—K) = 358.6-367.3 pm).
    Notes: Die neuen Verbindungen Cs6K3Sb[AlSb3] und Cs6K3Sb[GaSb3] entstehen aus stöchiometrischen Gemischen von Cs, AlSb (GaSb) und KSb in verschweißten Niob-Ampullen bei 950 K. Besonderes Merkmal der hexagonalen Strukturen sind eindimensionale Stabpackungen 1∞[Cs6K3Sb], gebildet aus Säulen kondensierter (Cs6K6/2)-Ikosaeder. Die Ikosaeder sind von Sb3---Anionen zentriert. Zwischen den Ikosaedersäulen sind die trigonal-planaren Anionen [AlSb3]6-- bzw. [GaSb3]6-- eingebettet. Sie werden durch die Alkalimetallatome koordiniert. Die FIR-Spektren können den Schwingungen der Anionen [MSb3]6-- mit der Symmetrie 6m2-D3h zugeordnet werden.(P63/mmc, Nr. 194; a = 1101,7 bzw. 1097,2 pm; c = 1158,9 bzw. 1150,1 pm; Z = 2; Einkristalldaten: 574 bzw. 546 Reflexe; R = 0,073 bzw. 0,029. Abstände: d(Al—Sb) = 265,4 pm; d(Ga—Sb) = 265,1 pm; d(Sb—Cs) = 401,6-423,0 pm; d(Sb—K) = 358,6-367,3 pm).
    Additional Material: 3 Ill.
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