Syntheses and characterization of novel three-dimensional tellurites, Na<inf>2</inf>MTe<inf>4</inf>O<inf>12</inf> (M = W, Mo), with intersecting tunnels

Two isostructural tellurium-rich tellurites, Na2WTe4O12 (1) and Na2MoTe4O12 (2), have been synthesized and structurally characterized by single-crystal X-ray diffraction studies. Three types of polyhedra, namely, MO6 octahedra, TeO3 pyramids, and TeO5 square-pyramids, constitute the three-dimensional (MTe4O12)2- (M = W, Mo) anionic framework, which contains different types of intersecting tunnels, one of them being novel spiral pseudohexagonal tunnels occupied by sodium ions. Both compounds have the monoclinic space group C2/c, with Z = 4. The lattice parameters are as follows: for 1, a= 17.348(3) Å, b = 5.7755(10) Å, c = 11.269(3) Å, β = 104.33(2)°; for 2, a = 17.341(4) Å, b = 5.8262(11) Å, c = 11.268(2) Å, β = 104.38(2)°. Syntheses and structure, powder X-ray diffraction, and infrared spectroscopic studies of these compounds are described. © 1999 American Chemical Society.