| Abstract
| - A novel open framework U−O material with composition (NH4)3(H2O)2{[(UO2)10O10(OH)][(UO4)(H2O)2]} was synthesized hydrothermally. The structure [monoclinic, a = 11.627(2)Å, b = 21.161(3) Å, c = 14.706(2) Å, β = 103.930(3)°, V = 3511.97 Å3] was solved by directmethods and refined on the basis of F2 for all 4230 unique reflections in space group C2/c toan agreement factor (R1) of 7.7%, calculated using 2180 unique observed reflections (|Fo| ≥4σF). The structure contains six symmetrically distinct U6+ sites, five of which occur asapproximately linear (UO2)2+ uranyl ions that are coordinated by four or five additionalligands, giving square and pentagonal bipyramids. One U6+ cation occurs in distortedoctahedral coordination. The structure contains β-U3O8-type sheets parallel to (001) thatare cross-linked through U2O12 pentagonal bipyramid dimers, resulting in an open frameworkstructure composed only of uranium polyhedra. The (NH4)+ and H2O groups are located inthe interconnected three-dimensional channels along [100] that are bounded by 10-memberedrings of uranyl polyhedra. A new layered uranyl material with composition Cs3[(UO2)3O2(OH)3]2Cl(H2O)3 was obtained by treatment of the framework phase in CsCl solution at 180 °C for33 h. The structure [monoclinic, space group C2, a = 19.615(5) Å, b = 7.239(2) Å, c = 12.064(3) Å, β = 127.929(4)°, V = 1351.2(6) Å3] was refined on the basis of F2 using 2462 uniquereflections to R1 = 7.2%, calculated using the 1800 unique observed reflections (|Fo| ≥ 4σF).The structure contains α-U3O8-type sheets of uranyl pentagonal bipyramids, with twosymmetrically distinct Cs cations, a single Cl anion, and two H2O groups located in theinterlayer regions.
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