inorganic compounds
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The crystal structure of Li2Na2NiP6O18·12H2O is characterized by the presence of six-membered P6O186− phosphate ring anions (internal symmetry -1) having a chair conformation and three different cations, viz. Li+, Na+ and Ni2+, to counterbalance the anionic charge. All atoms are in general positions except for nickel, which lies on a special position with site symmetry 2. Lithium has a tetrahedral environment (LiO4), and sodium and nickel have octahedral environments [NaO6 and Ni(H2O)6, respectively]. The P6O18 rings are linked via corner sharing by NaO6 octahedra and LiO4 tetrahedra to form a three-dimensional framework presenting tunnels running along [010] in which the six-coordinated Ni2+ cations are located. The structure is stabilized by a network of O—HO hydrogen bonds.
metal-organic compounds
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The title compound, (C3H12N2)[Cr2O7], consists of a discrete dichromate anion with an eclipsed conformation and a propane-1,3-diammonium cation. Both kinds of ions have a mirror plane passing through the bridging O atom and the central methylene C atom of the Cr2O72− and C3H12N22+ moieties, respectively. Anions and cations are alternately stacked to form columns parallel to the b axis. Ions are linked by intra- and inter-column hydrogen bonds of types N—HO and C—HO, involving O atoms of the dichromate anions as acceptors, and ammonium or methylene groups as donors.
organic compounds
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In the title hydrated molecular salt, 2C4H16N33+·P6O186−·2H2O, the complete cyclohexaphosphate anion is generated by crystallographic inversion symmetry. The six P atoms of the P6O186− anion form a chair conformation and the organic cation has a corrugated linear geometry. In the crystal, the cations and the anions are connected by N—HO hydrogen bonds into slabs propagating in the ac plane. The water molecules link the slabs by accepting N—HO links and forming O—HO links. The triclinic polymorph was reported by Gharbi et al. [(1995). J. Solid State Chem. 114, 42–51].