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Key indicatorsSingle-crystal X-ray study T = 298 K Mean (S-O) = 0.009 Å H-atom completeness 0% Disorder in main residue R factor = 0.037 wR factor = 0.035 Data-to-parameter ratio = 10.7For details of how these key indicators were automatically derived from the article, see Figure 1 Projection of the crystal structure of (I) on to the ac plane. inorganic papers i258 Abdelhedi et al. Cs 2 (SO 4 ) 0.57 (SeO 4 ) 0.43 ÁTe(OH) 6 Acta Cryst. (2005). E61, i256-i258

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Alkali-sulfate and selenate tellurate compounds having the formula M2XO4Te(OH)6 with (M= K, NH4, Tl and X= S, Se) have been crystallographically studied in order to examine the effect and the influence of cationic and/or anionic substitution over the crystalline symmetry and physical properties. The ammonium sulfate tellurate, (NH4)2SO4Te(OH)6, is monoclinic Cc, whereas the (NH4)2SeO4Te(OH)6 material crystallizes in the P21/c space group.1,2 On the other hand, the thallium sulfate tellurate Tl2SO4Te(OH)6 crystallizes in the P21/a space group. 3 We have been continuing our study of sulfate-selenate solid solutions of tellurate salts, among which we have reported Rb2[( S0.5Se0.5)O4]Te(OH)6 and Cs2 [(S0.57Se0.43)O4]Te(OH)6. 4,5 We have now prepared Tl2[(S0.6Se0.4)O4]Te(OH)6. In this study we clearly show the crystallographic differences and the effect of extensions of the anionic and cationic volume groups, which can help us to understand which, if any, geometrical features can be responsible for the electrical properties.Crystals of TlSSeTe were prepared at room temperature by the slow evaporation of an aqueous solution of a mixture of telluric acid, H6TeO6 (Aldrich, 99%), thallium carbonate Tl2C O3 (Aldrich 99.9%), selenic acid H2SeO4 (Aldrich 94%) and thallium sulfate Tl2SO4 (Aldrich 99.999%) at room temperature (The stoichiometric ratio is 1:0.5:0.5:0.5).Schematically the reactions are:Several recrystallizations were necessary to obtain single crystals suitable for an X-ray diffraction study. The composition of the obtained crystals was determined by chemical analysis, and confirmed by a crystal-structure refinement. A schematic diagram of the compound is shown in Fig. 1. The unit-cell dimensions were measured and refined using indexation of diffraction markings collected with a BrukerNonius X8-APEX2 CCD area-detector diffractometer using the APEX2 program. The structure of Tl2[(S0.6Se0.4)O4]Te(OH)6 was analyzed with the crystallographic CRYSTALS program. Density was measured, at room temperature, using the pycnometric method, by flotation in CCl4. The chemical crystal data, the parameters used for the X-ray diffraction data collection and the strategy used for the crystal structure determination and their results are listed in Table 1. The final positions and equivalent isotropic thermal parameters are given in Table 2. Hydrogen atoms were not determined. X-ray Structure Analysis Online Synthesis and Crystal

Structure D 2000Structural, Calorimetric and Conductivity Study of the New Mixed Solution Rb2(SO4)0.5(SeO4)0.5Te(OH)6. -Single crystals of the new mixed solid solution of title are obtained from an aq. solution of H6TeO6, Rb2SO4 and Rb2SeO4 upon slow evaporation. Rb2(SO4)0.5(SeO4)0.5Te(OH)6 crystallizes in the monoclinic space group P21/c with Z = 4. The structure is characterized by the presence of different independent anions in the same crystal , and ). The anions are arranged in a number of sheets of pure S/SeO4 tetrahedra alternating with sheets of pure Te(OH)6 octahedra. The structure is stabilized by OH···O hydrogen bonds which link tetrahedral and octahedral anions. DSC results show two anomalies at about 420 and 500 K, which are analyzed by dielectric measurements using the impedance spectroscopy technique. -(ABDELHEDI, M.; DAMMAK*, M.; COUSSON, A.; KOLSI, A. W.; J. Alloys Compd. 398 (2005) 1-2, 55-61; Lab. Chim. Inorg., Fac. Sci. Sfax, 3018 Sfax, Tunisia; Eng.) -Schramke 38-007 (SO 2-4 S eO 2-4 T eO 6-6