Isopropylammonium Layered Uranyl Chromates: Syntheses and Crystal Structures of [(CH3)2CHNH3]3[(UO2)3(CrO4)2O(OH)3] and[(CH3)2CHNH3]2[(UO2)2(CrO4)3(H2O)]

Two novel isopropylamine-templated uranyl chromates, [(CH3)2CHNH3]3[(UO2)3(CrO4)2O(OH)3] (1) and [(CH3)2CHNH3]2[(UO2)2(CrO4)3(H2O)] (2) were prepared by hydrothermal method at 100 degrees C. The compounds were characterized by electron microprobe analysis and X-ray diffraction crystal structure analysis [1: trigonal, P31m, a = 9.646(4), c = 8.469(4) angstrom, V = 682.4(5) angstrom 3; 2: monoclinic, P21/c, a = 11.309(3), b = 11.465(3), c = 17.055(5) angstrom, beta = 99.150(6)degrees, V = 2183.2(11) angstrom 3]. The structure of 1 is based upon trimers of uranyl bipyramids interlinked by CrO4 tetrahedra to form [(UO2)3(CrO4)2O(OH)3]3 layers, whereas, in the structure of 2, UO7 and UO6(H2O) pentagonal bipyramids are linked through CrO4 tetrahedra into the [(UO2)2(CrO4)3(H2O)]2 layers. The structures show many similarities to related uranyl selenate compounds, thus providing additional data on similarities and differences between uranyl sulfates, chromates, selenates, and molybdates.