Synthetic Strategies for the Synthesis of Ternary Uranium(IV) and Thorium(IV) Fluorides

Abstract

A series of new U(IV) and Th(IV) fluorides, NaUF (1), NaUF (2), NaUF (3), KThF (4), NaThF (5), (HO)ThF (6), and (HO)UF (7), was obtained using hydrothermal and low-temperature flux methods. Mild hydrothermal reactions with uranyl acetate as a precursor yielded 1, 7, and the monoclinic polymorph of NaUF, whereas direct reactions between UF and NaF led to the formation of 2 and orthorhombic NaUF (3). This highlights an unexpected difference in reaction products when different starting uranium sources are used. All seven compounds were characterized by single-crystal X-ray diffraction, and their structures are compared on the basis of cation topology, revealing a close topological resemblance between fluorides on the basis of the layers observed in NaUF(HO). Phase-pure samples of 1, 2, and both polymorphs of NaUF were obtained, and their spectroscopic and magnetic properties were measured. The UV-vis data are dominated by the presence of U cations and agree well with the electronic transitions. Effective magnetic moments of the studied compounds were found to range from 3.08 to 3.59 μ.

Supramolecular interaction-induced assemblies of polyanions and 2-aminopyridinium in two polyoxometalate-based hybrids

“…As shown in Fig. 6(c), the m À1 versus T curve above the ordering temperature reveals a clear region of linearity which fits the Curie-Weiss law m À1 = (T -)/C to data above 100 K for compound (II) with C = 1.09 emu K mol À1 and = À75.2 K. The negative value also agrees with the antiferromagnetic properties of compound (II) at high temperature (Klepov et al, 2018). The variations of magnetization with the magnetic field of compound (II) were also investigated at 3 K (Fig.…”

Expanding pentafluorouranates: hydrothermal synthesis and characterization of β-NaUF5 and β-NaUF5·H2O

“…A comparison between 2 and Na 4 CuU 6 F 30 U-F bond lengths can be found in ESI Table 3. † When the structures of 2 was rst obtained and 3 was identied as NaUF 5 in the literature, 12 it seemed unreasonable to expect two radically different structures with the same stoichiometry from the same reaction. In the same paper which published the structure of a-NaUF 5 , the structure of (H 3 O)U 3 F 13 was presented, the rst structurally-characterized hydronium uranium uoride, so a reevaluation of Na3 and Na4 in 2 was therefore considered, with the possibility that their larger volumes might indicate hydronium sites instead.…”

“…10,11 More recently, a number of ternary and quaternary hydrated, hydronium, alkali, and transition metal uranium uorides have been reported for potential applications as phases for separation of actinides or use in molten ux reactors. [12][13][14][15][16][17][18][19][20] These studies yielded the rst high-quality structural data of rhombohedral Na 7 U 6 F 31 , as well as the rst syntheses of NaUF 5 and NaU 2 F 9 . The development of the copper-catalyzed U 6+ /U 4+ in situ reduction step by Yeon, et al 19 has led to the production of over a dozen new ternary and quaternary uranium uorides, but the remarkable stability of Na 4 CuU 6 F 30 inhibited the production of sodium uranium uorides until recently.…”

The low-temperature barium fluoridozirconate variety α-BaZr2F10

“…In the homologous series MU 2 F 9 and MTh 2 F 9 (M = Na, K, Rb and Cs) (Olchowka et al, 2014;Klepov et al, 2018;Brunton, 1969;Yeon et al, 2014;Rosenzweig et al, 1973), characterized by UF 9 and ThF 9 polyhedra, it is interesting to note that for most alkaline cations, the formation of layers is absent or incomplete, corner sharing between MF 9 polyhedra of successive layers preventing their complete disconnection.…”