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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1614-1620 
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1686-1691 
    ISSN: 0044-2313
    Keywords: Sodium scandium fluoride ; cryolite structure ; tolerance factor ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Cryolite Structure of Na3ScF6 and the Tilting of Octahedra in Isostructural Sodium Hexafluorometallates Na3MF6X-ray studies at single crystals of Na3ScF6 confirmed the monoclinic cryolite type structure of this compound: a = 559.5, b = 580.2, c = 811.6 pm, β = 90.72°, Z = 2, space group P21/n; R1 = 0.021 for 512 symmetry independent reflections. The octahedra of [ScF6] (average Sc—F = 200.7 pm), as well as those of [NaF6] (Na1—F = 229.1 pm) linked to them, are titled by about 20° with respect to the axes of the perovskite-like pseudocell. This tilting of octahedra is discussed in comparison with other cryolites and with orthorhombic perovskites NaMF3; there results a correlation between tilt angle and tolerance factor t ˜ 0.88 of these compounds, the [NaF8] coordination of which invariably exhibits a constant mean value of Na2—F = 231.5 ± 1 pm for the four shortest distances.
    Notes: Eine röntgenographische Untersuchung an Einkristallen von Na3ScF6 bestätigte die monokline Kryolithstruktur dieser Verbindung: a = 559,5, b = 580,2, c = 811,6 pm, β = 90,72°, Z = 2, Raumgruppe P21/n; R1 = 0,021 für 512 symmetrie-unabhängige Reflexe. Die [ScF6]-Oktaeder (Mittelwert Sc—F = 200,7 pm) sind ebenso wie die mit ihnen verknüpften [NaF6]-Oktaeder (Na1—F = 229,1 pm) um etwa 20° gegen die Richtungen der perowskitartigen Pseudozelle gekippt. Diese Oktaederkippung wird im Vergleich mit anderen Kryolithen und mit den orthorhombischen Perowskiten NaMF3 diskutiert; dabei ergibt sich ein Zusammenhang zwischen Kippungswinkel und Toleranzfaktor t 〈 0,88 für diese Verbindungen, in deren [NaF8]-Koordination sich einheitlich ein konstanter Mittelwert von Na2—F = 231,5 ± 1 pm für die vier kürzesten Abstände zeigt.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1048-1054 
    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.
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