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  • Chemistry  (2)
  • Cesium copper(II) fluoride, CsCu2F5
  • Cyano-elpasolites
  • IR Spectra
  • Wiley-Blackwell  (2)
  • 1985-1989  (2)
  • 1975-1979
  • 1987  (1)
  • 1986  (1)
Collection
Keywords
  • Chemistry  (2)
  • Cesium copper(II) fluoride, CsCu2F5
  • Cyano-elpasolites
  • IR Spectra
  • Inorganic Chemistry  (2)
Publisher
  • Wiley-Blackwell  (2)
Years
  • 1985-1989  (2)
  • 1975-1979
Year
  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Single Crystal Structure Determinations of the Cubic High Pressure Elpasolites Rb2LiFeF6 and Cs2NaFeF6: Pressure-Distance Paradox without Change of Coordination NumberAt single crystals of metastable high pressure phases of Rb2LiFeF6 (a = 824.4 pm) and Cs2NaFeF6 (a = 873,9 pm) the parameters of the cubic elpasolite structure (Fm3m, Z = 4) were determined by X-ray methods. Compared to the 12L-structures of the normal pressure phases (R3m, hex. Z = 6) only the distances within the 12-coordination, Rb—F = 291.7 resp. Cs—F = 309.9 pm, are compressed by 2-3%. However, the octahedral distances Fe—F = 194.6 pm and Li—F = 217.6 pm resp. Fe—F = 194.9 pm and Na—F = 242.0 pm, are enlarged by 1-4%, though there was no increase in coordination number. This paradoxical behaviour is discussed. Difference Fourier syntheses reveal disorder only for the lithium positions in Rb2LiFeF6, which are 30 pm off-center, corresponding to a splitting of distances Li—F into 188, 247 and 4 × 220 pm.
    Notes: An Einkristallen der metastabilen Hochdruckphasen von Rb2LiFeF6 (a = 824,4 pm) und Cs2NaFeF6 (a = 873,9 pm) wurden röntgenographisch die Parameter der kubischen Elpasolithstruktur (Fm3m, Z = 4) bestimmt. Gegenüber den 12 L-Strukturen der Normaldruckphasen (R3m, hex. Z = 6) sind nur die Abstandswerte in der Zwölferkoordination, Rb—F = 291,7 bzw. Cs—F = 309,9 pm, um 2-3% verkleinert. Aber für die oktaedrischen Abstände Fe—F = 194,6 pm und Li—F = 217,6 pm bzw. Fe—F = 194,9 pm und Na—F = 242,0 pm ergeben sich Aufweitungen von 1-4%, obwohl keine Erhöhung der Koordinationszahl stattgefunden hat. Dieses paradoxe Verhalten wird diskutiert. Nur für die Lithiumpositionen in Rb2LiFeF6 zeigen Differenzfouriersynthesen eine Fehlordnung, die einer Li-Auslenkung von 30 pm aus dem Oktaederzentrum und einer Li—F-Abstandsaufspaltung in 188, 247 und 4 × 220 pm entspricht.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetragonal Fluoroperovskites AM0,75 □ 0,25F3 Deficient in Cations: K4MnIIM2IIIF12 and Ba2Cs2Cu3F12By heating 2KMnF3 + K2MnF6 and BaF2, CsF + CuF2 respectively, the isostructural tetragonal compounds K4Mn3F12 (a = 832.2, c = 1643.0 pm) and Ba2Cs2Cu3F12 (a = 854.1, c = 1704.1 pm) were prepared. They crystallize in a cation-deficient perovskite structure exhibiting ordering of octahedral vacancies. Single crystal structures determinations in the space group I41/amd, Z = 4, yielded the following average distances within the octahedra, which are Jahn-Teller distorted for MnIII and CuII:MnII—F = 208.3 pm, MnIII—F = 4 × 183.0/2 × 209.7 pm; Cu—F = 190.7/227.1 and 190.6/236.4 pm, respectively. The results are discussed in comparison with related compounds.
    Notes: Durch Erhitzen von 2KMnF3 + K2MnF6 bzw. von BaF2, CsF und CuF2 wurden die isostrukturellen tetragonalen Verbindungen K4Mn3F12 (a = 832,2, c = 1643,0 pm) bzw. Ba2Cs2Cu3F12 (a = 854,1, c = 1704,1 pm) hergestellt. Sie kristallisieren in einer kationendefizitären Perowskitstruktur mit geordneter Verteilung der zu einem Viertel unbesetzten Oktaederlücken. Die Einkristallstrukturbestimmungen in der Raumgruppe I41/amd, Z = 4, ergaben folgende mittlere Abstände in den für MnIII and CuII Jahn-Teller-verzerrten Oktaedern: MnII - F = 208,3 pm, MnIII—F = 4 × 183,0/2 × 209,7 pm; Cu—F = 190,7/227,1 bzw. 190,6/236,4 pm. Die Resultate werden im Vergleich mit verwandten Verbindungen diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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