K2Na8(UO2)8Mo4O24[(S,Mo)O4], the first uranium molybdosulfate: synthesis, crystal structure, and comparison to related compounds

Abstract

Orange platy crystals of K2Na8(UO2)8Mo4O24[(S,Mo)O4], the first known uranium molybdosulfate, have been prepared by high-temperature solid-state reactions. The structure (monoclinic, C2/c, a = 24.282(4), b = 12.1170(18), c = 13.6174(17) A, β = 106.33(1)o, V = 3845.0(9) A3, Z = 4) has been solved by direct methods and refined to R1 = 0.058 on the basis of 2837 unique observed reflections. The structure consists of a three-dimensional heteropolyhedral framework based upon the [(UO2)4O4(Mo2O10)] layers parallel to (010). The layers are formed by linkage of chains of edge-sharing UO7 bipyramids running along the c axis via the Mo2O10 dimers of edge-sharing MoO6 octahedra. Linkage of the layers into a three-dimensional framework is provided by the MoO4 and SO4 tetrahedra that share corners with the MoO6 octahedra. The Na+ and K+ cations reside in framework cavities in between the uranyl molybdate layers. The structure of K2Na8(UO2)8Mo4O24[(S,Mo)O4] is yet another complex derivative of the U2MoO8 structure type.