Expanding pentafluorouranates: hydrothermal synthesis and characterization of β-NaUF and β-NaUF·HO.

Two new sodium uranium(iv) pentafluorides were synthesized from uranium dioxide, HF, and NaF using mild hydrothermal conditions. β-NaUF·HO has greater lattice energy than previously-known α-NaUF·HO and possesses lower symmetry with the latter compound being orthorhombic, whereas β-NaUF·HO is monoclinic. Trigonal β-NaUF also possesses different connectivity between the [UF ] building units than the α-phase, with higher symmetry and greater lattice energy than orthorhombic α-NaUF. The single crystal absorption spectra of these compounds are also reported and compared.