Syntheses, Single-Crystal Structures, and Structural Chemistry of Hexafluoridouranates(V), MUF₆ (M = Li–Cs, Ag, Tl, H₃O), and the Dodecafluoridodiuranate(V) Ba[U₂F₁₂]·1.36HF

We present the syntheses of the hexafluoridouranates(V) MUF6 (M = Li–Cs, Ag, Tl, H3O) and of the dodecafluoridodiuranate(V) Ba[U2F12]·1.36HF. With the exception of AgUF6 and H3OUF6, all compounds were synthesized by reacting the respective metal fluorides with β-UF5 in anhydrous hydrogen fluoride (aHF). AgUF6 was obtained as a side product in the oxidation of Ag powder with UF6 under a CO atmosphere, while H3OUF6 was obtained from the controlled hydrolysis of β-UF5 with SiO2 in aHF. For this hydrolysis, silica glass wool proved to be the superior choice of SiO2. X-ray diffraction experiments on single crystals of the compounds as well as on polycrystalline samples allowed the unambiguous determination of their crystal structures, clarifying previously published structure models that were based on only powder X-ray diffraction. The structural chemistry of these compounds is discussed. In the case of LiUF6, NaUF6, and H3OUF6, molecular UF6– anions are observed in the solid state, while one-dimensional infinite strands of ∞1{[UF4/1F4/2]−} anions are present in the crystal structures of KUF6, RbUF6, TlUF6, and AgUF6. The dodecafluoridodiuranate(V) Ba[U2F12]·1.36HF is the second example of a compound containing the peculiar [U2F12]2– anion. Its U atoms show a coordination number of seven in a capped trigonal prismatic coordination sphere, and these prisms share a common edge. In contrast to the Sr homologue, the Ba compound contains HF molecules of crystallization.