Pentavalent Uranium Oxide via Reduction of [UO2]2+ Under Hydrothermal Reaction Conditions
Nebebech Belai, Mark Frisch, Eugene Ilton, Bruce D. Ravel, Christopher Cahill
The synthesis, crystal structure and spectroscopic characterization of [UV(H2O)2(UVIO2)2O4(OH)](H2O)4, a mixed-valent UV/UVI oxide material, are reported. The hydrothermal reaction of UO22+ with Zn and hydrazine at 120 °C for three days yields 1 in the form of a dark red crystalline solid. Compound 1 has been characterized by a combination of single-crystal and powder X-ray diffraction(XRD),elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy(XPS)and X-ray absorption spectroscopy(XAS). The structure consists of an extended sheet of edge and corner shared UVI pentagonal bipyramids that are further connected by edge sharing to square bipyramidal UV units. The overall topology is similar to the mineral ianthinite. The uranium L3-edge XAS revealed features consistent with those observed by single-crystal X-ray diffraction. High resolution XPS data analysis of the U4f region confirmed the oxidation states of U as originally assigned from XRD analysis and bond valence summations.