Combinatorial topology of uranyl molybdate sheets: syntheses and crystal structures of (C6H14N2)3[(UO2)5(MoO4)8](H2O)4 and (C2H10N2)[(UO2)(MoO4)2]

Two new mixed organic–inorganic uranyl molybdates, (C6H14N2)3[(UO2)5(MoO4)8](H2O)4 (1) and (C2H10N2)[(UO2)(MoO4)2] (2), have been obtained by hydrothermal methods. The structure of 1 [triclinic, <f>P1¯</f>, <f>Z=1</f>, <f>a=11.8557(9)</f>, <f>b=11.8702(9)</f>, <f>c=12.6746(9)</f> A˚, <f>α=96.734(2)°</f>, <f>β=91.107(2)°</f>, <f>γ=110.193(2)°</f>, <f>V=1659.1(2)</f> A˚] has been solved by direct methods and refined on the basis of F2 for all unique reflections to <f>R1=0.058</f>, which was calculated for the 5642 unique observed reflections (<f>|Fo|&ges;4σF</f>). The structure contains topologically novel sheets of uranyl square bipyramids, uranyl pentagonal bipyramids, and MoO4 tetrahedra, with composition [(UO2)5(MoO4)8]6−, that are parallel to (−101). H2O groups and 1,4-diazabicyclo [2.2.2]-octane (DABCO) molecules are located in the interlayer, where they provide linkage of the sheets. The structure of 2 [triclinic, <f>P1¯</f>, <f>Z=2</f>, <f>a=8.4004(4)</f>, <f>b=11.2600(5)</f>, <f>c=13.1239(6)</f> A˚, <f>α=86.112(1)°</f>, <f>β=86.434(1)°</f>, <f>γ=76.544(1)°</f>, <f>V=1203.14(10)</f> A˚] has been solved by direct methods and refined on the basis of <f>F2</f> for all unique reflections to <f>R1=0.043</f>, which was calculated for 5491 unique observed reflections (<f>|Fo|&ges;4σF</f>). The structure contains topologically novel sheets of uranyl pentagonal bipyramids and MoO4 tetrahedra, with composition [(UO2)(MoO4)2]2−, that are parallel to (110). Ethylenediamine molecules are located in the interlayer, where they provide linkage of the sheets. All known topologies of uranyl molybdate sheets of corner-sharing U and Mo polyhedra can be described by their nodal representations (representations as graphs in which U and Mo polyhedra are given as black and white vertices, respectively). Each topology can be derived from a simple black-and-white graph of six-connected black vertices and three-connected white vertices by deleting some of its segments and white vertices. [Copyright &y& Elsevier]