Elaboration, étude structurale et analyse CHARDI et BVS d’une nouvelle variété β-Na(9)Cr(MoO(4))(6) de type alluaudite

The title compound, nonasodium chromium(III) hexakis[molybdate(VI)], β-Na(9)CrMo(6)O(24), was prepared by solid-state reactions. This alluaudite-type structure is constituted of infinite layers formed by links between M (2)O(10) (M = C/Na) dimers and MoO(4) tetra­hedra. The Na(+) and Cr(3+) cations are located in the same site with, respectively, 0.25 and 0.75 occupancies. The layers are connected to each other through MoO(4) sharing corners, resulting an in open three-dimensional framework with hexa­gonal-form cavities occupied by Na(+) cations. The proposed structural model is supported by charge-distribution (CHARDI) and bond-valence-sum (BVS) analysis. All atoms are on general positions except for one Mo, two Na (site symmetry 2) and another Na site (site symmetry -1). A comparison is made with the similar structures Na(4)Co(MoO(4))(3), Na(2)Ni(MoO(4))(2), Cu(1.35)Fe(3)(PO(4))(3) and NaAgFeMn(2)(PO(4))(3).