Uranium(VI) Tetraoxido Core Coordinated by Bidentate Nitrate

Abstract

The synthesis and structural characterization of the compounds K[(UO(2))(2)(UO(4))(OH)(NO(3))(2)]H(2)O (1) and Ba[(UO(2))(4)(UO(4))(2)(OH)(2)(NO(3))(4)]H(2)O (2) have revealed that each contains sheets that are based upon the beta-U(3)O(8)-type topology and that these sheets are linked through low-valence interlayer cations. Consistent with other uranium(VI) compounds that have topologically identical sheets, one of the uranium(VI) sites exhibits a highly unusual (UO(4))(2-) tetraoxido core that is further coordinated by two bidentate (NO(3))(-) groups.

Uranyl Nitrates: By-Products of the Synthetic Experiments or Key Indicators of the Reaction Progress?

“…Crystallization of K[UO 2 (NO 3 ) 3 ] occurred in the system with the highest U:Cr molar ratio (6:1). The details of another system targeted to obtain novel uranyl chromates were reported in [52]. Crystallization of K[(UO 2 ) 2 (UO 4 )(OH)(NO 3 ) 2 ]H 2 O and Ba[(UO 2 ) 4 (UO 4 ) 2 (OH) 2 (NO 3 ) 4 ]H 2 O [52] occurred as the result of hydrothermal experiments in the presence of nitrate salts of K and Ba, respectively, and CrO 3 with the U:Cr molar ratio equal to 5:1.…”

“…The details of another system targeted to obtain novel uranyl chromates were reported in [52]. Crystallization of K[(UO 2 ) 2 (UO 4 )(OH)(NO 3 ) 2 ]H 2 O and Ba[(UO 2 ) 4 (UO 4 ) 2 (OH) 2 (NO 3 ) 4 ]H 2 O [52] occurred as the result of hydrothermal experiments in the presence of nitrate salts of K and Ba, respectively, and CrO 3 with the U:Cr molar ratio equal to 5:1. When the concentration of Cr in the systems increases up to 1:1, crystallization of uranyl-chromate-nitrates occurs [53], and when the ratio increases to c.a.…”

Nollmotzite, Mg[UV(UVIO2)2O4F3]·4H2O, the first natural uranium oxide containing fluorine

“…Morrison et al, 2011). Furthermore, in at least two reported structures (Wu et al, 2009;Unruh et al, 2010), [6] U 6+ adopts an unusual tetraoxido core, wherein the four equatorial bonds of the octahedra are short, $ 1.8 Å , and the axial bonds are longer, $ 2.3 Å . In contrast to U VI compounds, there are only a few well defined U V structures known.…”

Insight into the Uranyl Oxyfluoride Topologies through the Synthesis, Crystal Structure, and Evidence of a New Oxyfluoride Layer in [(UO2)4F13][Sr3(H2O)8](NO3)·H2O

“…The characteristic bond lengths in each U polyhedron are close to those traditionally found for U VI O 2 F 5 pentagonal bipyramids. 49 These four uranium polyhedra are connected to each other through fluorine corners to form cyclic tetrameric building blocks (Figure 1), which in turn share 53 where nitrate groups link readily to the uranium atoms, in our case, the nitrate groups were removed from the coordination of the uranyl ion and substituted by fluorine atoms. Powder X-ray diffraction data on crushed crystals and powder simulation ascertained the purity of the sample used for further analysis.…”

“…This linkage leads to an open framework with one-dimensional (1D) channels running along the [0 1 0] direction and accommodating free water molecules. It is worth noticing that, unlike recent work on uranyl nitrates by Unruh et al, where nitrate groups link readily to the uranium atoms, in our case, the nitrate groups were removed from the coordination of the uranyl ion and substituted by fluorine atoms. Powder X-ray diffraction data on crushed crystals and powder simulation ascertained the purity of the sample used for further analysis.…”