Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Sergey V. Krivovichev

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

Journal of Geosciences, volume 59 (2014), issue 2, 115 - 121

DOI: http://doi.org/10.3190/jgeosci.166

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) Å, β = 106.33(1)°, V = 3845.0(9) ų, 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.