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  • vibrational spectra  (2)
  • Alkali metal pnictido indates, -gallates  (1)
  • 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Alkali metal pnictido indates, -gallates ; crystal structures ; vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: K2NaGaP2, Cs2NaGaP2, K2NaGaAs2, K2NaInP2 and K2NaInAs2, Compounds with the Polyanions 1∞[MX4/2]3- (M=Ga, In; X=P, As) isosteric with SiS2The title compounds are synthesized from stoichiometric mixtures of the elements or from Na, KP(KAs), Cs4P6 and MX (M=Ga, In; X=P, As) at 950K. They are isotypic and crystallize in the space group Ibam (No. 72) with Z=4. The anionic partial structure is characterized by infinite chains 1∞[MX4/2]3- which are isosteric to SiS2. Vibrational spectra are measured and interpreted based on the symmetry D4h-P(2/m 2/c)42/m of the isolated polymer chain 1∞[MX2]3-. A good agreement between observed and calculated frequencies is obtained by using a force field of the tetrameric fragment [M4X10]18- (three four-membered M2X2 rings).
    Notes: Die Titelverbindungen werden aus den stöchiometrischen Gemischen der Elemente oder aber aus Na, KP(KAs) bzw. Cs4P6 und MX (M = Ga, In; X = P, As) bei 950 K dargestellt. Sie sind isotyp und kristallisieren in der Raumgruppe Ibam (Nr. 72) mit Z=4. Die anionische Partialstruktur ist durch unendliche Ketten 1∞[MX4/2]3- charakterisiert, isoster zu SiS2. Schwingungsspektren wurden gemessen und mit der Symmetrie D4h-P(2/m 2/c)42/m der isolierten Polymerkette 1∞[MX2]3- interpretiert. Eine gute Übereinstimmung zwischen den beobachteten und berechneten Frequenzen erhält man bei Verwendung des Kraftfeldes für das tetramere Fragment [M4X10]18- (drei M2X2-Vierringe).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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