Preparation and single-crystal structure of β-NH₄UF₅, ammonium pentafluoruranate(IV)

Hydrothermal Syntheses, Structures, and Magnetic Properties of the U(IV) Fluorides (C5H14N2)2U2F12·5H2O and (NH4)7U6F31

“…The oxidation of homopiperazine to diprotonated ethylenediamine and ammonium (and other unincorporated decomposition products) results in the formation of (C H N )U F (6) and (NH ) U F . Both of these compounds are insoluble in aqueous media and can be prepared independently of homopiperazine; it is important to note that the room temperature reaction of uranium compounds with #uoride in the presence of ammonium typically results in mixtures of (NH ) U F and -NH UF (18,27).…”

“…The F(6) atom in (NH ) U F was disordered over six closely spaced positions near the center of a cubooctahedral cavity. As the composition of this phase is known to be variable (18), the occupancy of the F(6) site was re"ned, converging to 0.13 (2). As re"nement on occupancy for determining chemical composition is questionable at best (20,21), the occupancy of this atom was set at 1/6, corresponding to the presence of exactly one F atom inside the cubooctahedral cavity.…”

“…The latter compound has been known since at least 1963 from X-ray powder di!raction data (17,18), but no further structural characterization has ensued.…”

Electronic Structure and Properties of Berkelium Iodates

“…In addition to changes in the dimensionality of the structure types, the local coordination environment of the M IV centers differs as well. In contrast to Zr­(IO 3 ) 4 , the Ce­(IO 3 ) 4 -structure type contains a MO 8 unit that conforms much closer to a trigonal dodecahedron ( D 2 d ) than a square antiprism ( D 4 d ). , Whether or not these distortions between different geometries of eight-coordinate metals reflect changing roles of metal orbitals in bonding has been debated for decades . However, there is computational evidence that supports this argument. , Extensive experimental and computational efforts are needed to confirm that different structures are actually manifestations of the divergent chemistry of different elements rather than subtle factors that influence crystallization.…”

Electronic, Magnetic, and Theoretical Characterization of (NH4)4UF8, a Simple Molecular Uranium(IV) Fluoride

“…Simple molecular fluorides such as these are uncommon, as only eight of over 50 ternary (M x U y F z ) and quaternary (M w M′ x U y F z ) uranium­(IV) structures (M, M′ = NH 4 + , group 1–13 metal ions, Ge 4+ , Sn 2+/4+ , Pb 2+/4+ , Sb 3+/5+ ) currently in the Inorganic Crystal Structure Database (ICSD) feature such distinct uranium environments. The remaining structures all feature corner-, edge-, or face-sharing structures and one- to three-dimensional topologies, most of which are held together by μ 2 bridging fluorides. ,,− One important exception is UF 6 , which sublimes at relatively mild temperature alongside homologue UCl 6 , due to weak van der Waals interactions between discrete octahedral molecules. , …”