Crystal structure of Li2 CaUF8

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. , …”

Application of a Mild Hydrothermal Approach Containing an in Situ Reduction Step to the Growth of Single Crystals of the Quaternary U(IV)-Containing Fluorides Na4MU6F30 (M = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+) Crystal Growth, Structures, and Magnetic Properties

“…12−17 Surprisingly, only a handful of quaternary uranium-containing fluorides, such as CaLi 2 UF 8 , have been reported. 18,19 Typically the U 4+ cations in these structures are found in large coordination environments of UF x (x = 7, 8, 9) polyhedra that lead to the formation of complex structure types. Remarkably, the total number of transition metal-containing uranium fluorides is very small, considering the importance of uranium as an element.…”

“…Uranium fluorides are an important group of materials that are fundamental for uranium separation processes, are potential materials for use in long-term nuclear waste storage, and can play a role in the development of new classes of fuel rod assemblies. − Not surprisingly, the binary uranium fluorides, such as UF 4 and UF 6 , have been extensively investigated and are currently being used in a variety of nuclear processes. − In addition, over 20 ternary inorganic uranium fluorides (other than minerals), such as alkali uranium fluorides and some transition metal uranium fluorides (Na 2 UF 6 , Na 3 UF 7 , K 3 UF 7 , CsU 2 F 9 , AuU 2 F 11 ) have been synthesized, and their structures were reported in the literature. − Surprisingly, only a handful of quaternary uranium-containing fluorides, such as CaLi 2 UF 8 , have been reported. , Typically the U 4+ cations in these structures are found in large coordination environments of UF x ( x = 7, 8, 9) polyhedra that lead to the formation of complex structure types. Remarkably, the total number of transition metal-containing uranium fluorides is very small, considering the importance of uranium as an element.…”

Trivalent Cation-Controlled Phase Space of New U(IV) Fluorides, Na3MU6F30 (M = Al3+, Ga3+, Ti3+, V3+, Cr3+, Fe3+): Mild Hydrothermal Synthesis Including an in Situ Reduction Step, Structures, Optical, and Magnetic Properties

“…Also, complex magnetic properties, especially when coupled with other magnetic ions, can be anticipated due to the presence of unpaired electrons in the 5f orbitals of U(IV). − We have focused on investigating a little-explored class of materials, that of the reduced solid-state uranium fluorides, because of their remarkable structural versatility − and important functions in the uranium separation and uranium oxide production processes. − Although a significant number of U(IV) fluorides have been reported, − ,− the majority of such compounds consist of ternary uranium fluorides; in other words, higher-order systems such as quaternary U(IV) fluorides have only rarely been prepared. In fact, only two quaternary compositions have been thoroughly structurally characterized, CaLiUF 8 , and Na 4 MU 6 F 30 (M = Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ), the latter of which was recently reported by our group. Moreover, the bulk of uranium fluoride research was conducted over 30 years ago, prior to the availability of routine single-crystal X-ray diffraction analysis and low-temperature magnetic measurements, underscoring the importance of a broad-based exploration of U(IV) fluoride chemistry utilizing modern characterization methods.…”

“…20−23 Although a significant number of U(IV) fluorides have been reported, 12−19,24−30 the majority of such compounds consist of ternary uranium fluorides; in other words, higher-order systems such as quaternary U(IV) fluorides have only rarely been prepared. In fact, only two quaternary compositions have been thoroughly structurally characterized, CaLiUF 8 31,32 and Na 4 MU 6 F 30 (M = Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ), 33 the latter of which was recently reported by our group. Moreover, the bulk of uranium fluoride research was conducted over 30 years ago, prior to the availability of routine singlecrystal X-ray diffraction analysis and low-temperature magnetic measurements, underscoring the importance of a broad-based exploration of U(IV) fluoride chemistry utilizing modern characterization methods.…”