LOW-TEMPERATURE SYNTHESES AND CHARACTERIZATION OF NOVEL LAYERED TELLURITES, A(2)MO(3)TEO(12) (A = NH4, CS), AND ZERO-DIMENSIONAL TELLURITES, A(4)MO(6)TE(2)O(24)-CENTER-DOT-6H(2)O (A = RB, K)

Hydrothermal synthetic investigations to prepare new A(2)Mo(3)TeO(12) (A = NH4, Cs, Rb, K) compounds are described Novel noncentrosymmetric layered tellurites, (NH4)(2)Mo3TeO12 (1) and Cs2Mo3TeO12 (2), have bee n synthesized by hydrothermal methods. Their structures contain two-di mensional hexagonal tungsten oxide related (Mo3TeO12)(2-) anionic laye rs interleaved with NH4+/Cs+ ions. New ''zero-dimensional'' tellurites , Rb4Mo6Te2O24. 6H(2)O (3) and K4Mo6Te2O24. 6H(2)O (4), containing dis crete centrosymmetric (Mo6Te2O24)(4-) anionic aggregates and alkali me tal ions have been synthesized by simple refluxing of stoichiometric r eactants in water. In this hexamolybdoditellurite anion, the Mo6O24 fl at hexagonal ring, formed from edge sharing of six MoO6 octahedra, is capped by tellurium on both sides. The two types of anions have the sa me empirical formula. Cs2Mo3TeO12 (2) could be prepared by a solid sta te reaction as well. All four new tellurites have been structurally ch aracterized by single-crystal X-ray diffraction studies. Pertinent cry stal, data are as follows: for 1, hexagonal space group P6(3), a = 7.3 32(2) Angstrom, c = 12.028(4) Angstrom, Z = 2: for 2, hexagonal space group P6(3), a = 7.3956(10) Angstrom, c = 12.186(2) Angstrom, Z = 2; f or 3, monoclinic space group P2(1)/c. a = 10.0564(14) Angstrom, b = 9. 877(8) Angstrom, c = 15.724(3) Angstrom, beta = 109.988(11)degrees; Z = 2: for 4, monoclinic space group P2(1)/c, a = 9.878(3) Angstrom, b = 9.724(4) Angstrom, c = 15.301(3) Angstrom, beta = 108.57(2)degrees, Z = 2. Low-temperature syntheses, structure, and powder X-ray diffracti on, spectroscopic, and thermal studies of compounds 1-4 are described.