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  • [FeO5] square pyramide  (1)
  • disodium metal(II) vanadium(III) heptafluorides  (1)
  • 1995-1999  (2)
  • 1
    ISSN: 0044-2313
    Keywords: Structure determination ; [FeO5] square pyramide ; asymmetric [PbO6] coordination ; lone pair effect ; perovskite relation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Lead Strontium Ferrate(III): The Crystal Structure of the Phase Pb4Sr2Fe6O15At orthorhombic single crystals of Pb4Sr2Fe6O15 (a = 568.73(8), b = 392.03(4), c = 2107.5(3) pm; Z = 4/3, space group Pnma) a X-ray structure determination has been performed (R1 = 0,036 for 488 „observed“ resp. wR2 = 0,073 for all 643 independent reflexions). It revealed a framework of polyhedra related to perovskite, in which chains of edgesharing pyramids [FeO5] (average Fe1—O: 197 pm; Fe1—Fe1: 305.5 pm) are linked via apices with corner-sharing [FeO6] octahedra (Fe2—O: 201 pm). 12-fold, strongly distorted cuboctahedrally coordinated „perovskite positions“ show mixed occupancy by 2/3 Sr + 1/3 Pb (= Sr2; Sr2—O: 287 pm). More spacy channels, running parallel to the chains of pyramids along [010] of the structure, contain lead atoms only. The double occupancy of the corresponding cages results in short distances Pb1—Pb1 (355.9 pm) and Pb1—Fe2 (314.4 pm), as well as in a very asymmetric [PbO6] coordination (Pb1—O: 253 pm), in the opposite hemisphere of which the lone electron pair s2 is supposed to be located. Details are communicated and structural relations discussed.
    Notes: An orthorhombischen Einkristallen von Pb4Sr2Fe6O15 (a = 568,73(8), b = 392,03(4), c = 2107,5(3) pm; Z = 4/3, Raumgruppe Pnma) wurde eine Röntgenstrukturbestimmung durchgeführt (R1 = 0,036 für 488 „beobachtete“ bzw. wR2 = 0,073 für alle 643 unabhängigen Reflexe). Diese ergab ein perowskitverwandtes Polyedergerüst, in dem Ketten kantenverknüpfter [FeO5]-Pyramiden (Mittelwert Fe1—O: 197 pm; Fe1—Fe1: 305,5 pm) mit ihrerseits eckenverknüpften [FeO6]-Oktaedern (Fe2—O: 201 pm) über Ecken verbunden sind. Zwölffach, stark verzerrt kuboktaedrisch koordinierte „Perowskit-Positionen“ sind gemischt besetzt mit 2/3 Sr + 1/3 Pb (= Sr2; Sr2—O: 287 pm). Dagegen befinden sich in größeren Kanälen, die sich parallel zu den Pyramidenketten längs [010] durch die Struktur ziehen, nur Bleiatome. Die doppelte Besetzung der zugehörigen Hohlräume führt zu kurzen Abständen Pb1—Pb1 (355,9 pm) und Pb1—Fe2 (314,4 pm), und zu einer ganz einseitigen [PbO6]-Koordination (Pb1—O: 253 pm). in deren Gegenhemisphäre das s2-Elektronenpaar zu vermuten ist. Einzelheiten werden mitgeteilt und Strukturverwandtschaften diskutiert.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Structure determination ; vanadium weberites ; disodium metal(II) vanadium(III) heptafluorides ; sodium tetrafluoro-vanadate(III) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Crystal Structures of the Vanadium Weberites Na2MIIVIIIF7 (MII = Mn, Ni, Cu) and of NaVF4At single crystals of the vanadium(III) compounds NaVF4 (a = 790.1, b = 531.7, c = 754.0 pm, β = 101.7°; P21/c, Z = 4), Na2NiVF7 (a = 726.0, b = 1031.9, c = 744.6 pm; Imma, Z = 4) and Na2CuVF7 (a = 717.6, b = 1043.5, c = 754.6 pm; Pmnb, Z = 4) X-ray structure determinations were performed, at Na2MnVF7 (a = 746.7, c = 1821.6 pm; P3221, Z = 6) a new refinement. NaVF4 crystallizes in the layer structure type of NaNbO2F2. The fluorides Na2MIIVF7 represent new orthorhombic (MII = Ni; Cu) resp. trigonal (MII = Mn) weberites. The average distances within the [VF6] octahedra of the four compounds are in good agreement with each other and with data of related fluorides (V—F: 193.3 pm). The differences between mean bond lengths of terminal and bridging F ligands are 5% in NaVF4, but less than 1% in the weberites. Details and data for comparison are discussed.
    Notes: An Einkristallen der Vanadium(III)-Verbindungen NaVF4 (a = 790,1, b = 531,7, c = 754,0 pm, β = 101,7°; P21/c, Z = 4), Na2NiVF7 (a = 726,0, b = 1031,9, c = 744,6 pm; Imma, Z = 4) und Na2CuVF7 (a = 717,6, b = 1043,5, c = 754,6 pm; Pmnb, Z = 4) wurden Röntgenstrukturbestimmungen durchgeführt, an Na2MnVF7 (a = 746,7, c = 1821,6 pm; P3221, Z = 6) eine neue Verfeinerung. NaVF4 kristallisiert in der Schichtstruktur des NaNbO2F2-Typs. Die Fluoride Na2MIIVF7 sind neue orthorhombische (MII = Ni; Cu) bzw. trigonale (MII = Mn) Weberit-Vertreter. Die mittleren Abstände in den [VF6]-Oktaedern der vier Verbindungen stimmen gut miteinander und mit Daten in verwandten Fluoriden überein (V—F: 193,3 pm). Die Unterschiede zwischen den mittleren Abständen terminaler und verbrückender F-Liganden betragen in NaVF4 5%, in den Weberiten aber weniger als 1%. Einzelheiten und Vergleichsdaten werden diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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