Hydrothermal synthesis and crystal structure of Cs{sub 6}[(UO{sub 2}){sub 4}(W{sub 5}O{sub 21})(OH){sub 2}(H{sub 2}O){sub 2}]: a new polar uranyl tungstate
- Department of Chemistry, Auburn University, Auburn, Alabama 36849 (United States)
The hydrothermal reaction of UO{sub 3}, WO{sub 3}, and CsIO{sub 4} leads to the formation of Cs{sub 6}[(UO{sub 2}){sub 4}(W{sub 5}O{sub 21})(OH){sub 2}(H{sub 2}O){sub 2}] and UO{sub 2}(IO{sub 3}){sub 2}(H{sub 2}O). Cs{sub 6}[(UO{sub 2}){sub 4}(W{sub 5}O{sub 21})(OH){sub 2}(H{sub 2}O){sub 2}] is the first example of a hydrothermally synthesized uranyl tungstate. It's structure has been determined by single-crystal X-ray diffraction. Crystallographic data: tetragonal, space group I4cm, a=15.959(2)A, c=14.215(1)A, Z=4, MoK{alpha}, {lambda}=0.71073A, R(F)=2.84% for 135 parameters with 2300 reflections with I>2{sigma}(I). The structure is comprised of two-dimensional {sub {infinity}}{sup 2}[(UO{sub 2})4(W{sub 5}O{sub 21})(OH){sub 2}(H{sub 2}O){sub 2}]{sup 6-} anionic layers that are separated by Cs{sup +} cations. The coordination polyhedra found in the novel layers consist of UO{sub 7} pentagonal bipyramids, WO{sub 6} distorted octahedra, and WO{sub 5} square pyramids. The UO{sub 7} polyhedra are formed from the binding of five equatorial oxygen atoms around a central uranyl, UO{sub 2}{sup 2+}, unit. Both bridging and terminal oxo ligands are employed in forming the WO{sub 5} square pyramidal units, while oxo, hydroxo, and aqua ligands are found in the WO{sub 6} distorted octahedra. In the layers, four (UO{sub 2})O{sub 5} polyhedra corner share with equatorial oxygen atoms to form a U{sub 4}O{sub 24} tetramer entity with a square site in the center; a tungsten atom populates the center of each of these sites to form a U{sub 4}WO{sub 25} pentamer unit. The pentamer units that result are connected in two dimensions by edge-shared dimers of WO{sub 6} octahedra to form the two-dimensional {sub i}nfinity{sup 2}[(UO{sub 2}){sub 4}(W{sub 5}O{sub 21})(OH){sub 2}(H{sub 2}O){sub 2}]{sup 6-} layers. The lack of inversion symmetry in Cs{sub 6}[(UO{sub 2}){sub 4}(W{sub 5}O{sub 21})(OH){sub 2}(H{sub 2}O){sub 2}] can be directly contributed to the WO{sub 5} square pyramids found in the pentamer units. In the structure, all of these polar polyhedra align their terminal oxygens in the same orientation, along the c axis, thus resulting in a polar compound.
- OSTI ID:
- 20653391
- Journal Information:
- Journal of Solid State Chemistry, Vol. 177, Issue 10; Other Information: DOI: 10.1016/j.jssc.2004.07.028; PII: S0022-4596(04)00415-3; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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