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Dimensional Reduction in Alkali Metal Uranyl Molybdates: Synthesis and Structure of Cs 2 [(UO 2 )O(MoO 4 )]
Author(s) -
Alekseev Evgeny V.,
Krivovichev Sergey V.,
Armbruster Thomas,
Depmeier Wulf,
Suleimanov Evgeny V.,
Chuprunov Evgeny V.,
Golubev Alexei V.
Publication year - 2007
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200700270
Subject(s) - uranyl , molybdate , alkali metal , crystallography , orthorhombic crystal system , tetrahedron , ionic bonding , metal , ionic radius , chemistry , molybdenum , materials science , crystal structure , inorganic chemistry , ion , organic chemistry
A new uranyl molybdate, Cs 2 [(UO 2 )O(MoO 4 )] ( 1 ), has been prepared by high‐temperature solid‐state reactions. The structure has been solved by direct methods and refined to R 1 = 0.0284 for | F 0 | ≥4σ F . The compound 1 is orthorhombic, Pca 2 1 , a = 12.018(2), b = 12.438(2), c = 17.917(3) Å, V = 2678.2(7) Å 3 , Z = 12. The structure of 1 is based upon one‐dimensional chains consisting of corner‐sharing UO 6 and MoO 4 polyhedra. The UO 6 square bipyramids share cis equatorial vertices to form zigzag chains that are further stabilized by bidendate MoO 4 tetrahedra. The chains have composition [(UO 2 )O(MoO 4 )] 2− and are oriented parallel to the c axis. In the structure, adjacent chains form pseudo‐2D‐layers parallel to (010). The Cs + cations are in between the pseudolayers. The composition‐structure relationships in alkali metal uranyl molybdates can be rationalized from the viewpoint of dimensional reduction using the following assumptions: (1) representation of the A x U n Mo m O y formula (n ≤ m) as a sum of UMoO 6 (= UO 2 MoO 4 ), A 2 O, and A 2 MoO 4 (A = alkali metal): A x U n Mo m O y = kA 2 O + nUMoO 6 + (m‐n)A 2 MoO 4 , where x = 2(k + m − n) and y = k + 2n + 4m; (2) analysis of the dimensionality of uranyl molybdate structural units and its changes upon incorporation of ionic reagents A 2 O and A 2 MoO 4 into a parent framework of UO 2 MoO 4 that consists of 3‐D array of U and Mo based polyhedra. The relationships between different compositions and structures may be visualized using the UO 2 MoO 4 –A 2 O–A 2 MoO 4 compositional diagram. The observed trends of decreasing dimensionality of the uranyl molybdate units allow to specify on this diagram fields of dimensionality.