inorganic compounds
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In comparison with the previous structure determination of the β-modification of barium catena-polyphosphate that was based on Weissenberg film data [Grenier et al. (1967). Bull. Soc. Fr. Minéral. Cristallogr. 90, 24–31], the current CCD-data-based redetermination reveals all atoms with anisotropic displacement parameters, standard uncertainties for the atomic coordinates, and the determination of the absolute structure. Moreover, a much higher accuracy in terms of the bond-length distribution for the polyphosphate chain, with two shorter and two longer P—O distances, was achieved. The structure consists of polyphosphate chains extending parallel to [100] with a periodicity of two PO4 tetrahedra. The Ba2+ cations are located between the chains and are surrounded by ten O atoms in the form of a distorted coordination polyhedron, with Ba—O distances ranging from 2.765 (3) to 3.143 (3) Å, also reflecting the higher precision of the current redetermination.
research communications
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The basic building units of the hydrous periodate Pb3(IO4(OH)2)2 are three Pb2+ cations and two IO4(OH)23− anions. The octahedral anions are arranged in a distorted hexagonal rod packing, with the cations (each with a coordination number of eight) located in between.
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2,5-Diazido-1,4-phenylene diacetate and dibutyrate are the first structurally characterized representatives with a trans-diazidophenylene entity. Both molecules possess inversion symmetry; however, the compounds crystallize in different crystal systems (triclinic versus monoclinic).
research communications
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The crystal structure of [NiHg(SCN)4(CH3OH)2]n is made up of HgS4 tetrahedra and trans-NiN4O2 octahedra, linked together by thiocyanato bridges. The methanol molecules point to the cavities of the resulting framework.
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The crystal structures of the 1.5- and 10-hydrates of Na2SeO4 are isotypic with those of the corresponding chromates.
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The central ternary N atoms in the isotypic crystal structures of the substituted anilines show no sign of pyramidalization.
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Crystal structure of trans-1,4-bis[(trimethylsilyl)oxy]cyclohexa-2,5-diene-1,4-dicarbonitrile
The molecular structure of the title compound is centrosymmetric. The cyclohexa-2,5-diene moiety is exactly planar and has a bond-length distribution characteristic for one pair of double bonds and two pairs of single bonds.