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Paul Arthur Giesting, Nathan J. Porter, Peter Carman Burns
Uranyl oxalate hydrates: structures and IR spectra
Keywords: Uranyl oxalate, Hydrothermal synthesis, Infrared spectroscopy, Single crystal structure analysis, X-ray diffraction
The novel compound (UO2)2C2O4(OH)2(H2O)2 (UrOx2A) and the previously studied compound UO2C2O4(H2O)3 (UrOx3) have been synthesized by mild hydrothermal methods. Single crystal diffraction data collected at 125 K using MoKα radiation and a CCD-based area detector were used to solve and refine the crystal structures by full-matrix least-squares techniques to agreement indices (UrOx2A, UrOx3) wR2 = 0.037, 0.049 for all data, and R1 = 0.015, 0.024 calculated for 1285, 2194 unique reflections respectively. The compound UrOx2A is triclinic, space group P-1, Z = 1, a = 5.5353(4), b = 6.0866(4), c = 7.7686(6) Å, α = 85.6410(10)°, β = 89.7740(10)°, γ = 82.5090(10)°, V = 258.74(3) Å3. The compound UrOx3 is monoclinic, space group P21/c, Z = 4, a = 5.5921(4), b = 16.9931(13), c = 9.3594(7) Å, β = 99.5330(10)°, V = 877.11(11) Å3. The structures consist of chains of uranyl pentagonal bipyramids connected by oxalate groups and, in UrOx2A, hydroxyl groups; UrOx2A is also notable for its high (2 : 1) ratio of uranyl to oxalate groups, higher than any observed in other published structures of uranyl oxalates. The structure determined for UrOx3, previously studied by Jayadevan and Chackraburtty (1972); Mikhailov et al. (1999) is in agreement with the previous results; however, the increased precision of the present low-temperature structure refinement allows for the assignment of H atom positions based on the difference Fourier map of electron density. The infrared spectra of these two materials collected at room temperature are also presented and compared with previous work on uranyl oxalate systems.
Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0044-2968
Volume: 221, 04/2006
Pages: 252 - 259