Hydrothermal synthesis and crystal structures of new uranyl oxalate hydroxides: {alpha}- and {beta}-[(UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(OH){sub 2}(H{sub 2}O){sub 2}] and [(UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(OH){sub 2}(H{sub 2}O){sub 2}].H{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)
Two modifications of the new uranyl oxalate hydroxide dihydrate [UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(OH){sub 2}(H{sub 2}O){sub 2}] (1 and 2) and one form of the new uranyl oxalate hydroxide trihydrate [(UO{sub 2}){sub 2}(C{sub 2}O{sub 4})(OH){sub 2}(H{sub 2}O){sub 2}].H{sub 2}O (3) were synthesized by hydrothermal methods and their structures determined from single-crystal X-ray diffraction data. The crystal structures were refined by full-matrix least-squares methods to agreement indices R(wR)=0.0372(0.0842) and 0.0267(0.0671) calculated for 1096 and 1167 unique observed reflections (I>2{sigma}(I)), for {alpha} (1) and {beta} (2) forms, respectively and to R(wR)=0.0301(0.0737) calculated for 2471 unique observed reflections (I>2{sigma}(I)), for 3. The {alpha}-form of the dihydrate is triclinic, space group P1-bar , Z=1, a=6.097(2), b=5.548(2), c=7.806(3)A, {alpha}=89.353(5), {beta}=94.387(5), {gamma}=97.646(5){sup o}, V=260.88(15)A{sup 3}, {beta}-form is monoclinic, space group C2/c, Z=4, a=12.180(3), b=8.223(2), c=10.777(3)A, {beta}=95.817(4), V=1073.8(5)A{sup 3}. The trihydrate is monoclinic, space group P2{sub 1}/c, Z=4, a=5.5095(12), b=15.195(3), c=13.398(3)A, {beta}=93.927(3), V=1119.0(4)A{sup 3}. In the three structures, the coordination of uranium atom is a pentagonal bipyramid composed of dioxo UO{sub 2}{sup 2+} cation perpendicular to five equatorial oxygen atoms belonging to one bidentate oxalate ion, one water molecule and two hydroxyl ions in trans configuration in 2 and in cis configuration in 1 and 3. The UO{sub 7} polyhedra are linked through hydroxyl oxygen atoms to form different structural building units, dimers [U{sub 2}O{sub 10}] obtained by edge-sharing in 1, chains [UO{sub 6}]{sub {approx}} and tetramers [U{sub 4}O{sub 26}] built by corner-sharing in 2 and 3, respectively. These units are further connected by oxalate entities that act as bis-bidentate to form one-dimensional chains in 1 and bi-dimensional network in 2 and 3. These chains or layers are connected in frameworks by hydrogen-bond arrays.
- OSTI ID:
- 20784781
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 11; Other Information: DOI: 10.1016/j.jssc.2005.08.018; PII: S0022-4596(05)00393-2; 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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