Structures and syntheses of layered and framework amine-bearing uranyl phosphate and uranyl arsenates

Two hydrated uranyl arsenates and a uranyl phosphate were synthesized by hydrothermal methods in the presence of amine structure-directing agents and their structures determined: (N2C6H14)[(UO2)(AsO4)]2(H2O)3, DabcoUAs, <f>{NH(C2H5)3}[(UO2)2(AsO4)(AsO3OH)]</f>, TriethUAs, and (N2C4H12)(UO2)[(UO2)(PO4)]4(H2O)2, PiperUP. Intensity data were collected at room temperature using MoKα X-radiation and a CCD-based area detector. The crystal structures were refined by full-matrix least-squares techniques on the basis of <f>F2</f> to agreement indices (DabcoUAs, TriethUAs, PiperUP) <f>wR2=5.6%</f>, 8.3%, 7.2% for all data, and <f>R1=2.9%</f>, 3.3%, 4.0%, calculated for 1777, 5822, 9119 unique observed reflections (<f>|Fo|⩾4σF</f>), respectively. DabcoUAs is monoclinic, space group <f>C2/m</f>, <f>Z=2</f>, <f>a=18.581(1)</f>, <f>b=7.1897(4)</f>, <f>c=7.1909(4)</f> Å, <f>β=102.886(1)°</f>, <f>V=936.43(9)</f> Å3, <f>Dcalc=3.50</f> g/cm3. TriethUAs is monoclinic, space group <f>P21/n</f>, <f>Z=4</f>, <f>a=9.6359(4)</f>, <f>b=18.4678(7)</f>, <f>c=10.0708(4)</f> Å, <f>β=92.282(1)°</f>, <f>V=1790.7(1)</f> Å3, <f>Dcalc=3.41</f> g/cm3. PiperUP is monoclinic, space group Pn, <f>Z=2</f>, <f>a=9.3278(4)</f>, <f>b=15.5529(7)</f>, <f>c=9.6474(5)</f> Å, <f>β=93.266(1)°</f>, <f>V=1397.3(1)</f> Å3, <f>Dcalc=4.41</f> g/cm3. The structure of DabcoUAs contains the autunite-type sheet formed by the sharing of vertices between uranyl square bipyramids and arsenate tetrahedra. The triethylenediammonium cations are located in the interlayer along with two H2O groups and are disordered. Both TriethUAs and PiperUP contain sheets formed of uranyl pentagonal bipyramids and tetrahedra (arsenate and phosphate, respectively) with the uranophane sheet-anion topology. In TriethUAs, triethlyammonium cations are located in the interlayer. In PiperUP, the sheets are connected by a uranyl pentagonal bipyramid that shares corners with phosphate tetrahedra of adjacent sheets, resulting in a framework with piperazinium cations and H2O groups in the cavities of the structure. [Copyright &y& Elsevier]