UO(2)(C(2)H(3)O(2))(2).2H(2)O reacts with AX or A(C(2)H(3)O(2) or ClO(4)) (where A = Li, Na, K; X = Cl, Br) and crown ethers in HCl or HBr aqueous solutions to give the sandwich-type compounds [K(18-crown-6)](2)[UO(2)Cl(4)] (1), [K(18-crown-6)](2)[UO(2)Br(4)] (2), [Na(15-crown-5)](2)[UO(2)Cl(4)] (3), [Na(15-crown-5)](2)[UO(2)Br(4)] (4), [Li(12-crown-4)](2)[UO(2)Cl(4)] (5), and [Li(12-crown-4)](2)[UO(2)Br(4)] (6). The compounds have been characterized by single-crystal X-ray diffraction, powder diffraction, elemental analysis, IR, and Raman spectroscopy. The [UO(2)X(4)](2-) ions coordinate to two [A(crown)](+) cations through the four halides only (2), through two halides only (3), through the two uranyl oxygens and two halides (3, 4), or through the two uranyl oxygen atoms only (5, 6). Raman spectra reveal nu(U-O) values that correlate with expected trends. The structural trends are discussed within the context of classical principles of hard-soft acid-base theory.

Post closure radioactive release scenarios from geologic salt formation, such as the WIPP (Waste Isolation Pilot Plant) (USA) include hydrologic transport of radionuclides through a chloride saturated aquifer. Consequently, the understanding of actinide solution chemistry in brines is essential for modeling requiring accurate knowledge of the interaction between AnO22+ and chloride ions. Complexation constants of two U(VI) chloride species UO2Cl+ and UO2Cl20 have been intensively studied for about 40 years using different methods. However, large uncertainties reflect the general difficulty in determining accurate stability constants of weak complexes. In order to model the behavior of U(VI) in brines, we studied the formation of its chloride complexes by UV-Vis spectroscopy as a function of the NaCI concentration at 25 °C. The experiments were performed at constant ionic strength by varying the concentration ratio of NaCI and NaClO4. Deconvolution resulted in single component absorption sepectrum for UO2Cl+ and UO2Cl20. The apparent stability constants of UO2Cl+ and UO2Cl20 are determined at different ionic strengths. The experimental data are used to parameterize using the SIT approach.

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structure structure (solids and liquids) D 2000 41 -002 Coordination Trends in Alkali Metal Crown Ether Uranyl Halide Complexes: The Series [A(Crown)] 2 [UO 2 X 4 ] Where A: Li, Na, K and X: Cl, Br. -Title compounds (III), (V), and (VII) are characterized by powder and single crystal XRD and by IR and Raman spectroscopy. (III) and (Va) crystallize in the monoclinic space group P2 1 /n with Z = 2, (Vb) in the orthorhombic space group Pccn (Z = 4), (VIIa) in the orthorhombic space group Fmm2 (4), and (VIIb) is also orthorhombic (Cmca, 4). The coordination of the [UO 2 X 4 ] 2− ions to two [M + (crown)] cations each occurs via four halides in (III), via two halides for one orientation of (Va), via two halides and two uranyl oxygens in (Va) and (Vb), and via only the two uranyl oxygens in (VIIa,b). The structural trends are discussed within the context of classical principles of hard/soft acid-base theory. -(DANIS, JANET A.; LIN, MAVIS R.; SCOTT, BRIAN L.; EICHHORN, BRYAN W.; RUNDE, WOLFGANG H.; Inorg.