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metal-organic compounds
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The title compound, [Tl4(C4H9O)4], featuring a (Tl—O)4 cube, crystallizes with a quarter-molecule (located on a special position of site symmetry ..) and a half-molecule (located on a special position of site symmetry 23.) in the asymmetric unit. The Tl—O bond distances range from 2.463 (12) to 2.506 (12) Å. All O—Tl—O bond angles are smaller than 90° whereas the Tl—O—Tl angles are wider than a rectangular angle.
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inorganic compounds
The ternary compound tetrathallium diniobium undecaselenide, Tl4Nb2Se11, was prepared by a molten flux method from a melt of Tl2Se, elemental Se and Nb. The structure is composed of discrete Tl+ cations and complex [Nb2Se11]4- anions. In the anion, the two crystallographically independent Nb atoms are sevenfold coordinated by Se atoms to form a distorted pentagonal bipyramid. Two NbSe7 polyhedra have a face in common, thus yielding the [Nb2Se11]4- unit. The crystal structure of Tl4Nb2Se11 is isotypic with the structure of the homologous tantalum compound Tl4Ta2Se11 [Teske et al. (2002). Z. Anorg. Allg. Chem. 628, 2651-2655], which was the first polyselenide with discrete complex [M2Se11]4- anions.
metal-organic compounds
The two Ni atoms and the μ6-1,2,4,5-benzenetetracarboxylate ligand in the crystal structure of catena-[μ6-1,2,4,5-benzenetetracarboxylato-tetraaqua-dinickel(II)] dihydrate, [Ni2(C10H2O8)(H2O)4]·2(H2O), occupy special positions at three independent inversion centers. One of the Ni atoms is chelated by two 1,2,4,5-benzenetetracarboxylates [Ni—O 2.018 (3) and 2.021 (3) Å; O—Ni—O 91.7 (1)°]; the two remaining sites of the coordination octahedron of this atom are taken up by water molecules. The second Ni atom is coordinated by four carbonyl O atoms belonging to four benzenetetracarboxylate ligands [Ni—O 2.045 (3), 2.069 (3) Å]; its coordination sphere also includes two water molecules. Each tetraanionic benzenetetracarboxylate ligand links together six Ni atoms, the linkages giving rise to a three-dimensional network motif. The structure is consolidated by hydrogen bonds involving coordinated as well as uncoordinated water molecules.
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