The crystal chemistry of uranyl compounds containing tetrahedrally coordinated hexavalent cations is diverse owing to the variability in coordination geometries and linkage of polyhedra. Uranyl tungstates are an interesting group of compounds with the potential to exhibit novel topologies. W6+ occurs in various coordination numbers (4, 5 and 6), and the larger coordination numbers permit uranyl tungstates to form high dimensional topologies. Here we report the structure and characterization of new uranyl tungstates containing cation-cation interactions obtained by hydrothermal synthesis between 220 and 265 �C and their relationships with other actinide materials.  A cation-cation interaction in actinide chemistry is where an O atom of an actinyl ion coordinates a second actinyl ion.  These interactions are common for pentavalent actinides, but account for only about 2% of the structures of U(VI) uranyl compounds.  Where present, cation-cation interactions permit a closer-packed structure with higher density, and favor formation of framework structures.

Cation-cation interactions in uranyl tungstates

243rd National Meeting (2012)

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