The crystal and molecular structure of uranyl oxalate trihydrate

Abstract

Uranyl oxalate trihydrate, UOzCzO4.3H20, crystals are monoclinic with lattice parameters a = 5.623 (5), b=17.065 (2), c=9.451 (3)/~ and ,8=98.74 (1) °. The space group is P21/C with Z=4. 513 visually estimated reflexions were corrected for absorption and the structure refined by Fourier and least-squares methods to R = 0"079. Each uranium atom exists as a linear (O-U-O) 2+ ion with five secondary oxygen atoms coordinated to it in a perpendicular plane. The average distances are U-O~= 1-63 (4) and U-On = 2"49 (4)/~. The oxalate groups are planar and tetradentate, each bridging two uranyl ions. Only one water molecule is coordinated to the uranium atom. The structure is consistent with the thermal behaviour of the compound.

Structure Determination of Uranium Halogenide Phosphates UXPO4·2H2O (X=Cl, Br) from Powder Diffraction Data

“…5, the environment of the heavy atom may be viewed as a distortion of the known pentagonal bipyramidal arrangement (D F ) found in a number of well-defined uranium (IV, VI) compounds, e.g., UBr (21). This distortion is a consequence of the larger size of the halogen atom with respect to the four oxygen atoms that lie in the same plane.…”

Adaptable coordination of U(IV) in the 2D-(4,4) uranium oxalate network: From 8 to 10 coordinations in the uranium (IV) oxalate hydrates

“…The knowledge of actinide oxalate properties can also contribute to model the migration of radionucleides in the environment because the most important mechanism is the complexation of radionucleides by carboxylic functional groups of bacterial humic acids [1]. Since uranium is oxidized by atmospheric oxygen into uranium (VI), the crystal chemistry of uranyl containing oxalates has been extensively studied and is rather rich [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In contrast U(IV) oxalates have been less investigated although, in some oxalate precipitating processes, U(IV) is stabilized in nitric solution, after adding an anti-nitrous agent such as hydrazinium nitrate (N 2 H 5 + , NO 3 À ) to the solution.…”

Hydrothermal synthesis and crystal structures of new uranyl oxalate hydroxides: α- and β-[(UO2)2(C2O4)(OH)2(H2O)2] and [(UO2)2(C2O4)(OH)2(H2O)2]·H2O

“…A lot of work, devoted to the combination of uranyl cation UO 2 2+ and oxalate ligand C 2 O 4 2À , in the presence of monovalent cation M + (M + ¼ Na + , K + , N 2 H 5 + or NH 4 + ), have investigated various UO 2 2+ /C 2 O 4 2À ratios and permitted to solve some original structures [26][27][28][29][30][31][32][33][34][35][36]. The oxalate ions can act as monodentate, bidentate, tridentate or tetradentate chelating ligand and lead to the formation of several types of arrangements: (1) [26], in which oxalate ions are nonbridging, (2) dimeric isolated anions containing two uranium atoms when two bidentate oxalate anion are non-bridging and one links the two (UO 2 ) 2+ ions, in When available, single crystals of the compounds were all prepared from slow evaporation from solutions.…”