Synthèse et étude structurale de Na(9)Cr(MoO(4))(6)

The title compound, nona­sodium chromium(III) hexa­kis[molybdate(VI)], Na(9)Cr(MoO(4))(6) was prepared by solid-state reactions. The basic structure units are isolated polyhedral clusters composed of a central CrO(6) octa­hedron sharing vertices with six MoO(4) tetrahedra to form an open framework in which the Na(+) cations are bound to the free vertices of the MoO(4) tetra­hedra. The Cr(3+) cation has site symmetry of 32 (6a), one Na atom sits on a twofold axis (18e), and all other atoms are at general positions. The bond-valance-sum model confirms the expected values of ion charges. The title compound is isotypic with Na(9)Sc(MoO(4))(6) and Na(9)Fe(MoO(4))(6). It is compared and discussed with similar structures.