U(IV)/Ln(III) unexpected mixed site in polymetallic oxalato complexes. Part I. Substitution of Ln(III) for U(IV) from the new oxalate (NH{sub 4}){sub 2}U{sub 2}(C{sub 2}O{sub 4}){sub 5}.0.7H{sub 2}O
- Laboratoire de Cristallochimie et Physicochimie du Solide, UMR CNRS 8012, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d'Ascq Cedex (France)
- Laboratoire de Chimie des Actinides, CEA VALRHO/DRCP/SCPS, Bat 399 BP 17171, 30208 Bagnols sur Ceze Cedex (France)
A new ammonium uranium (IV) oxalate (NH{sub 4}){sub 2}U{sub 2}(C{sub 2}O{sub 4}){sub 5}.0.7H{sub 2}O (1) and three mixed uranium (IV)-lanthanide (III) oxalates (N{sub 2}H{sub 5}){sub 2.6}U{sub 1.4}M{sub 0.6}(C{sub 2}O{sub 4}){sub 5}.xH{sub 2}O (M=Nd (2) and M=Sm (3)), Na{sub 2.56}U{sub 1.44}Nd{sub 0.56}(C{sub 2}O{sub 4}){sub 5}.7.6H{sub 2}O (4) and Na{sub 3}UCe(C{sub 2}O{sub 4}){sub 5}.10.4H{sub 2}O (5), have been prepared. The crystal structures of compounds 1, 4 and 5 have been determined by single-crystal X-ray diffraction. The crystal structures were solved by the direct methods and Fourier difference techniques, and refined by a least square method on the basis of F{sup 2} for all unique reflections. Compounds 2 and 3 are isotypic with 1. Crystallographic data: 1, hexagonal, space group P6{sub 3}/m mc, a=19.177(3), c=12.728(4)A, Z=6, R{sub 1}=0.0575 for 52 parameters with 1360 reflections with I>=2{sigma}(I); 2, hexagonal, space group P6{sub 3}/mmc, a=19.243(4), c=12.760(5)A, Z=6; 3, hexagonal, space group P6{sub 3}/mmc, a=19.211(3), c=12.274(4)A, Z=6; 4, orthorhombic, space group Pbcn, a=18.79(3), b=11.46(1), c=12.77(2)A, Z=4, R{sub 1}=0.0511 for 183 parameters with 3026 reflections with I>=2{sigma}(I); 5, monoclinic, space group C2/c, a=18.878(6), b=11.684(4), c=12.932(4)A, {beta}=95.97(1){sup o}, Z=4, R{sub 1}=0.0416 for 213 parameters with 4060 reflections with I>=2{sigma}(I). The honeycomb-like structure of the five compounds is built from the same three-dimensional arrangement of metallic and oxalate ions. Similar hexagonal rings of alternating metallic and oxalate ions form layers parallel to the (001) plane that are pillared by another oxalate ion. Indeed, some torsions or rotations of the bridging oxalate ligands led to modifications of the network symmetry. The monovalent cations and the water molecules occupy the hexagonal tunnels running down the [001] direction. Starting from the uranium (IV) compound A{sub 2}U{sub 2}(C{sub 2}O{sub 4}){sub 5}.0.7H{sub 2}O with A=NH{sub 4}{sup +} (1), the mixed U(IV)/Ln(III) oxalates are obtained by partial substitution of U(IV) by Ln(III) in a ten-coordinated site, the charge deficit being compensated by intercalation of supplementary monovalent ions within the tunnels. The distortion of the arrangement in the [001] direction for the Na-containing compounds allows the accommodation of a greater number of water molecules that insure an octahedral coordination of the Na atoms.
- OSTI ID:
- 20721725
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 10; Other Information: DOI: 10.1016/j.jssc.2005.06.031; PII: S0022-4596(05)00297-5; Copyright (c) 2005 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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