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Article

Pentavalent Uranium Oxide via Reduction of [UO₂]²⁺ Under Hydrothermal Reaction Conditions^†

Supporting Info

Nebebech Belai^‡, Mark Frisch^‡, Eugene S. Ilton^§, Bruce Ravel^∥ and Christopher L. Cahill*^‡^⊥

Department of Chemistry, George Washington University, 725 21st Street N.W., Washington, D.C. 20052, Pacific Northwest National Laboratory, Chemical and Material Science Division, MSIN: K8-96, 902 Battelle Boulevard, Richmond, Washington 99352, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015

Inorg. Chem., 2008, 47 (21), pp 10135–10140

DOI: 10.1021/ic801534m

Publication Date (Web): October 9, 2008

‡

George Washington University.

Pacific Northwest National Laboratory.

∥

National Institute of Standards and Technology.

* To whom correspondence should be addressed. E-mail: Cahill@gwu.edu.

⊥

Carnegie Institution of Washington.

Abstract

The synthesis, crystal structure, and spectroscopic characterization of [U^V(H₂O)₂(U^VIO₂)₂O₄(OH)](H₂O)₄ (1), a mixed-valent U^V/U^VI 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 U^VI pentagonal bipyramids that are further connected by edge sharing to square bipyramidal U^V units. The overall topology is similar to the mineral ianthinite. The uranium L_|||-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.