Amine-templated uranyl selenates with layered structures. I - Structural diversity of sheets with a U : Se ratio of 1 : 2

Crystals of four amine-templated layered uranyl selenates, [C2H10N2][(UO2)(SeO4)(2)(H2O)](H2O) (1), [CH6N3](2)[(UO2)(SeO4)(2)(H2O)](H2O)(1.5) (2), [C4H12N](2)[(UO2)(SeO4)(2)(H2O)] (3), and [CH6N3](3)[(UO2)(2)(SeO4)(2)(H(SeO4)(2))](H2O)(2) (4) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amine. The structures of all four compounds have been solved by direct methods. The structures of 1 (monoclinic, C2/c, a 11.787(2), b = 7.7007(10), c = 16.600(3) angstrom, beta = 102.016(14)degrees, V 1473.7(4) angstrom(3), R-1 = 0.037 for 1743 unique observed reflections), 2 (monoclinic, C2/c, a = 37.314(4), b = 7.1771(6), c = 13.2054(14) angstrom, beta = 109.267(8)degrees, V = 3338.4(6) angstrom(3), R-1 = 0.088 for 3005 unique observed reflections) and 3 (monoclinic, C2/c, a = 27.212(10), b = 7.372(3), c = 23.113(7) angstrom, beta = 117.75(2)degrees, V= 4103(3) angstrom(3), R-1 = 0.073 for 2111 unique observed reflections) are based on sheets of the composition [(UO2)(SeO4)(2)(H2O)](2-) consisting of pentagonal [UO7](8-) pentagonal bipyramids linked via [SeO4](2-) tetrahedra. The sheets have the same chemical composition but different topologies. The structure of 4 (orthorhombic, P2(1)2(1)2(1), a = 10.7261(9), b = 13.918(2), c = 18.321(2) angstrom, V = 2735.1(5) angstrom(3), R-1 = 0.050 for 5683 unique observed reflections) contains [(UO2)(2)(SeO4)(2)(H(SeO4)(2))](3-) sheets parallel to (001). In all four structures, the layers are connected via protonated amine and H2O molecules.