Synthesis and crystal structure of bis(tetramethylammonium) aquotetra-fluorodioxouranate(VI) dihydrate, [(CI3)4 N]2[UO2 F4(H2 O)]·2H2O

Solvent Effects on Uranium(VI) Fluoride and Hydroxide Complexes Studied by EXAFS and Quantum Chemistry

“…The UO 2 (OH) 4 2- complex is an exception, having a square bipyramid geometry in the solid state . The corresponding tetrafluoride complex has also been studied in the solid state using single-crystal X-ray diffraction and was found to have the more common pentagonal bipyramid geometry by coordination of H 2 O. The same structures seem to be retained also in solution, as indicated by EXAFS data for the hydroxide system ,, and data on the fluoride system presented in this study.…”

“…The data were treated using the EXAFSPAK software. Theoretical backscattering phase and amplitude functions used in data analysis were calculated for the model complexes UO 2 F 4 (H 2 O) 2- and UO 2 F 5 3- using the known crystal structures , and the FEFF7 program . The MS path O−U−O (four-legged path) of the linear UO 2 2+ unit was included in the model fitting.…”

“…In one of our previous investigations we used quantum chemical methods as a tool to obtain a more detailed insight into the structure and dynamics of solution chemical systems . In this study we will explore the chemistry of the U(VI)−fluoride system using EXAFS and previous X-ray data . We will also compare the structure and bonding in uranium(VI) fluoride and hydroxide complexes by using different wave function and DFT based methods, both with and without the inclusion of models for the solvent.…”

Structure and Spectra of UO2F2 and Its Hydrated Species

“…There are a number of X-ray crystallographic studies of monomeric, dimeric, and trimeric uranyl compounds containing both fluoride ions and water molecules, with many not having water molecules bound to the uranyl moieties. For such monomeric uranyl complexes with a water molecule in the equatorial position, there is an X-ray study and an EXAFS study . Standard equatorial distances are 36 2.23 Å for U−F and 2.35 Å for U−OH 2 ; H bonding with more distant molecules affects these values noticeably .…”

“…For such monomeric uranyl complexes with a water molecule in the equatorial position, there is an X-ray study and an EXAFS study . Standard equatorial distances are 36 2.23 Å for U−F and 2.35 Å for U−OH 2 ; H bonding with more distant molecules affects these values noticeably . We used density functional methods to study trends in the structures, vibrational frequencies, and binding energies of UO 2 F 2 complexes with 2−4 equatorial water molecules.…”