Synthesis and Crystal Structures of New Layered Uranyl Compounds Containing Dimers [(UO2)(2)O-8] of Edge-Linked Pentagonal Bipyramids

Two new U(VI) compounds, [((CH3)(2)CHNH3)(CH3NH3)][(UO2)(2)(CrO4)(3)] (1) and [CH3NH3][(UO2) (SO4)(OH)] (2), were prepared by combining hydrothermal synthesis with isothermal evaporation. Compound 1 crystallizes in the monoclinic system, space group ?2(1), a = 9.3335(19), b = 10.641(2), c = 9.436(2) angstrom, = 94.040(4)degrees. Compound 2 crystallizes in the rhombic system, space group ?bca, a = 11.5951(8), b = 9.2848(6), c = 14.5565(9) angstrom. The structures of the compounds were solved by the direct methods and refined to R-1 = 0.041 [for 5565 reflections with Fo > 4 sigma(Fo)] and 0.033 [for 1792 reflections with Fo > 4 sigma(Fo)] for 1 and 2, respectively. Single crystal measurements were performed at 296 and 100 K for 1 and 2, respectively. The crystal structure of 1 is based on [(UO2)(2)(CrO4)(3)](2-) layers, and that of 2, on [(UO2)(SO4)(OH)](-) layers. Both kinds of layers are constructed in accordance with a common principle and are topologically similar. Protonated isopropylamine and methylamine molecules are arranged between the layers in 1, and protonated methylamine molecules, in 2. Compound 1 is the second known example of a U(VI) compound templated with two different organic molecules simultaneously.