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  • 1
    ISSN: 0044-2313
    Keywords: Dilithium magnesium tetrachloride ; dilithium vanadium tetrachloride ; dilithium cadmium tetrachloride ; crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal Structures of MgCrO4-type Li2VCl4 and Spinel-type Li2MgCl4 and Li2CdCl4The crystal structures of the ternary lithium chlorides Li2MCl4 (M = Mg, V, Cd) have been determined firstly by X-ray single-crystal experiments. Li2MgCl4 and Li2CdCl4 crystallize in an inverse spinel structure (space group Fd3m, Z = 8, a = 1 040.1(2) and 1 062.06(9) pm, structural parameters u = 0.25699(2) and 0.2550(1), R = 1.7 and 3.7% for 218 and 211 unique reflections). The Li—Cl distances of the tetrahedrally coordinated Li+ ions are significantly greater than calculated with Shannon's crystal radii ( 〉 238 ± 1 instead of 233 pm). Contrary to the results of X-ray powder data reported in the literature, Li2VCl4 crystallizes in the distorted spinel structure of MgCr2O4 type (space group F43m, Z = 8, a = 1 037.49(2) pm, R = 5.9% for 217 unique reflections). The decrease of the site symmetry of the octahedrally coordinated ions (V2+, Li+) from 3m to 3m resulting in contracted and widened tetrahedral M4 entities of the spinel structure is obviously caused by V—V metal - metal bonds (shortest V—V distance 366.2(7) pm).
    Notes: Die Kristallstrukturen der ternären Lithiumchloride Li2MCl4 (M = Mg, V, Cd) wurden mittels Röntgen-Einkristallmessungen bestimmt. Li2MgCl4 und Li2CdCl4 kristallisieren in einer inversen Spinell-Struktur (Raumgruppe Fd3m, Z = 8, a = 1 040,1(2) und 1 062,06(9) pm, Lageparameter u = 0,25699(2) bzw. 0,2550(1), R = 1,7 bzw. 3,7% bei 218 bzw. 211 symmetrieunabhängigen Reflexen). Die Li—Cl-Abstände der tetraedrisch koordinierten Li+-Ionen sind signifikant größer als erwartet ( 〉 238 ± 1 anstatt 233 pm). Li2VCl4 kristallisiert entgegen Literaturangaben in der verzerrten Spinell-Struktur des MgCrO4-Typs (Raumgruppe F43m, Z = 8, a = 1 037,49(2) pm, R = 5,9% bei 217 symmetrieunabhängigen Reflexen). Die Erniedrigung der Lage-Symmetrie der oktaedrisch koordinierten Ionen (V2+, Li+) von 3m nach 3m, die alternierend zu einer Kontraktion und einer Aufweitung der tetraedrischen M4-Baueinheiten der Spinell-Struktur führt, wird von V—V—Metall - Metall-Bindungen verursacht (kürzester V—V-Abstand 366,2(7) pm).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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