Expanding pentafluorouranates: hydrothermal synthesis and characterization of β-NaUF 5 and β-NaUF 5 ·H 2 O.

Two new sodium uranium(iv) pentafluorides were synthesized from uranium dioxide, HF, and NaF using mild hydrothermal conditions. β-NaUF 5 ·H 2 O has greater lattice energy than previously-known α-NaUF 5 ·H 2 O and possesses lower symmetry with the latter compound being orthorhombic, whereas β-NaUF 5 ·H 2 O is monoclinic. Trigonal β-NaUF 5 also possesses different connectivity between the [UF n ] building units than the α-phase, with higher symmetry and greater lattice energy than orthorhombic α-NaUF 5 . The single crystal absorption spectra of these compounds are also reported and compared.