Crystal structure of uranyl tetranitrates

Insights into the Structural Chemistry of Anhydrous and Hydrous Hexavalent Uranium and Neptunium Dinitrato, Trinitrato, and Tetranitrato Complexes

“…This is in contrast to the description provided by Gundu Rao et al , for the same composition and also isostructural A 2 [UO 2 - trans -(NO 3 ) 4 ]. ( A = NH 4 , Rb, Cs). − In these, the UO 8 polyhedra also have six equatorial oxygen positions originating from two monodentate and two bidentate NO 3 – ligands. However, instead of the mono- and bidentate ligands being cis to each other relative to the equatorial plane of the UO 8 polyhedra as shown in this study, they are trans (Figure d).…”

“…However, instead of the mono- and bidentate ligands being cis to each other relative to the equatorial plane of the UO 8 polyhedra as shown in this study, they are trans (Figure d). This difference in coordination motif about the central U atom between that described here for K 2 [UO 2 - cis -(NO 3 ) 4 ] in comparison to previous studies − is suspected to contribute to the dramatic difference in unit cell volume. Interestingly, despite this significant difference in unit cell volume between the previous − and current investigations, the reported structures are both in identical monoclinic space groups.…”

“…This difference in coordination motif about the central U atom between that described here for K 2 [UO 2 - cis -(NO 3 ) 4 ] in comparison to previous studies − is suspected to contribute to the dramatic difference in unit cell volume. Interestingly, despite this significant difference in unit cell volume between the previous − and current investigations, the reported structures are both in identical monoclinic space groups. Thus, the relationship between this novel anhydrous ternary hexavalent tetranitrato complex and that of a previous study is best described as related geometrical isomers rather than polymorphs.…”

“…The unit cell volume was determined to be 1187.4(4) Å 3 with a = 9.1565(18) Å, b = 15.002(2) Å, c = 8.6460(15) Å, and β = 91.176(17)°. Pertinently, the unit cell volume of K 2 [UO 2 - cis -(NO 3 ) 4 ] is found to be nearly double that described for the previously reported isostructural compositions A 2 [UO 2 (NO 3 ) 4 ] ( A = K, NH 4 , Rb, Cs), hereafter denoted A 2 [UO 2 - trans -(NO 3 ) 4 ]. − K 2 [UO 2 - cis -(NO 3 ) 4 ] consists of isolated U cations that are coordinated by eight oxygen atoms, forming UO 8 hexagonal-bipyramidal polyhedra with short axial oxo U–O bonds of length 1.72(2) and 1.74(2) Å characteristic of the uranyl group. The six equatorially coordinating oxygens to uranium are provided by two bidentate NO 3 – and two monodentate NO 3 – ligands.…”

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

“…From the crystal-chemical point of view, it means that two H 2 O molecules, which were arranged between the edge-shared nitrate groups in the equatorial plane of Ur in the structure of 5 are replaced during the dehydration process by two NO 3 groups, each of which has a common vertex with U 6+ atom. The topology belongs to the cc0-1:4-2 type, and is rather common, being found in the structures of nine organically templated compounds and four inorganic uranyl nitrates (e.g., [28][29][30][31]).…”