Crystal chemistry of uranyl molybdates.: VI.: New uranyl molybdate units in the structures Of CS4[(UO2)3O(MoO4)2(MoO5)] and Cs6[(UO2)(MoO4)4]

Two Cs uranyl molybdates, CS4[(UO2)(3)O(MoO4)(2)(MoO5)] and Cs-6[(UO2)(MoO4)(4)], have been synthesized by high-temperature solid-state reactions. The structures of these compounds were solved by direct methods and refined on the basis of F-2 for all unique data collected with monochromatic MoKalpha X-radiation and a CCD (charge-coupled device) detector. The structure Of Cs-4[(UO2)(3)O(MoO4)(2)(MoO5)] was refined to an agreement factor (RI) of 4.4%, calculated using the 4873 unique observed reflections (F-o greater than or equal to 4sigma(F)). It is triclinic, space group P1, a 7.510(2), b 7.897(2), c 9.774(2) Angstrom, alpha 79.279(5), beta 81.269(5), gamma 87.251(5)degrees, V 562.8(2) Angstrom(3), Z = 1. The structure of Cs-6[(UO2)(MoO4)(4)] was refined to an R I of 4.9%, calculated using the 4275 unique observed reflections (F-o greater than or equal to 4sigma(F)). It is triclinic, space group P (1) over bar, a 11.613(3), b 12.545(3), c 14.466(3) Angstrom, alpha 102.713(6), beta 95.281(6), gamma 106.182(6)degrees, V 1947.7(8) Angstrom(3), Z = 3. These compounds are based upon uranyl molybdate structural units not previously observed in uranyl compounds. The structure Of Cs-4[(UO2)(3)O(MoO4)(2)(MoO5)] contains sheets of composition [(UO2)(3)Mo3O14](4-) that contain UrO(5) pentagonal bipyramids (Ur: uranyl ion), MoO4 tetrahedra and MoO5 polyhedra. The sheets are parallel to (100) and Cs cations are located in the interlayer. The structure Of Cs-6[(UO2)(MoO4)(4)] is based upon two symmetrically distinct finite clusters of composition [(UO2)(MoO4)(4)](6-), each of which contains a central UrO(4) square bipyramid that shares all four of its equatorial vertices with MoO4 tetrahedra. Three-dimensional connectivity is provided by Cs cations located between the clusters.