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December 2000 issue
inorganic compounds
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In the title compound, the V atom is sandwiched between two sulfate groups by corner-sharing to form a discrete [VO2(SO4)2(OH2)2]3− anion. The water molecules occupy cis positions in the equatorial plane of the vanadium octahedron.
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The new non-linear optical crystals LiKB4O7 and LiRbB4O7 contain two kinds of anionic groups, namely (B3O8)7− and (B5O10)5−. The (B3O8)7− chains parallel to the [100] direction are interconnected by sharing O atoms with (B5O10)5− groups.
metal-organic compounds
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organic compounds
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electronic papers (inorganic compounds)
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The crystal structure of low-temperature Na4Ti5O12 has been determined and refined from X-ray and neutron powder diffraction data at 295 K. The O and Na atoms form a distorted close-packed structure, where Ti atoms occupy octahedral sites.
electronic papers (metal-organic compounds)
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Amido complexes of titanium are useful reagents in a variety of syntheses and as precursors for chemical vapor deposition of TiN. The title compound crystallizes with one molecule in the asymmetric unit. The neutral complex shows an unusual fivefold coordination of the titanium centre.
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The central structural motif of the [Ti2(SC6H5)9]− anion features a face-sharing bi-octahedron. The charge is balanced by a [Li(C4H8O)4]+ cation.
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The title compound has a doubly methoxo-bridged centrosymmetric copper dimer cation involving two tridentate bis(pyrazolyl)amine ligands. The geometry of each CuII atom is a distorted square pyramid. The Cu⋯Cu distance is 3.058 (1) Å.
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In the title complex, the U atom is surrounded by seven O atoms giving a distorted pentagonal bipyramidal geometry. The U—Ouranyl and U—Odbm distances (dbm is 1,3-diphenylpropane-1,3-dionate) are in the ranges 1.760 (6)–1.776 (5) and 2.308 (4)–2.417 (4) Å, respectively, while the U—Osulfoxide distance is 2.427 (4) Å.
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In the title compound, both central Ag and B atoms lie on twofold axes and exhibit tetrahedral geometries. There seems to be no trigonal–tetrahedral disorder, as is prevalent in the analogous Au complex.
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The previously unknown title compound is a centrosymmetric linear trinuclear nickel(II) complex, where the Ni atoms are in an octahedral coordination and the ligand heteroatoms act so as to model amino acid residues.
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The title compound contains two Sn atoms in the asymmetric unit, that complexed by NMP exhibiting an octahedral and the other showing a trigonal–bipyramidal geometry. The most important features are three different Sn—Br bond lengths at both Sn atoms.
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In the title complex, the Pb centre has a distorted octahedral coordination with four μ2-Br ligands and two bridging 4,4-bipyridine (bipy) ligands in trans positions. The bipy group acts as a linear bifunctional bridge forming chains in the direction of the b axis. Pairs of bridging bromides join these into two-dimensional layers.
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The structure of the title compound at 150 K is essentially identical to that determined at room temperature, with the expected reduction in cell-axis length.
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In the title compound, a distorted octahedral CoIII complex shows an orientational disorder such that the positions of the nitro and aqua ligands are exchanged. As a result, the averaged structure has an inversion centre at the Co atom.
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In the title compound, a distorted octahedral CoIII complex shows an orientational disorder such that the positions of the nitro and chloro ligands are exchanged with 84:16% occupancy. The O atoms of the nitrate ion are disordered over two sites.
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In the title compound, two independent CoIII complexes with a distorted octahedral coordination show an orientational disorder. As a result, the averaged structure has inversion centres at the Co atoms. The perchlorate O atoms are disordered over two sites.
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The structure of the title compound has been determined and shows structural parameters comparable to those of the previously reported 3,5-bis(trifluoromethyl)pyrazole analogue.
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The title complex forms a three-dimensional network directed by alternating hydrogen-bonding and π–π interactions.
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The title molecule is dimeric and the O atoms of the trimethylsiloxy groups bridge the two Al atoms to form a four-membered ring.
electronic papers (organic compounds)
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The title compound is the product of the addition reaction of TiBr4 with 2-methylpyridine. It can be described as a slightly distorted trigonal bipyramid. The crystal structure is isomorphous with that of the tetrachloro analogue.
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The title molecule has approximate Cs symmetry. The dithiane ring adopts a chair conformation with the acetyl substituent in an axial orientation. A weak intermolecular C—H⋯O hydrogen bond (H⋯O 2.39 Å) involves the H atom at the 2-position of the ring.
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Myoporum bontioides is a folk medicinal plant from the northwest of China. The EtOH extract from the dried root of Myoporum bontioides was chromatographed to give furanoeudesmane-B. The relative stereochemistry has been determined.
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A culture of the fungus Pestalotiopsis microspora provided the natural product terrein. The crystal structure, for a sample obtained from methanol solution, is dominated by intermolecular hydrogen bonds.
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An intramolecular hydrogen bond between N atoms of the imidazole and pyridine moieties is responsible for the non-extended conformation of lansaprazole. Intermolecular N—H⋯O hydrogen bonding between imidazole and sulfinyl groups results in chains along the b axis.
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The title compound is the key synthetic intermediate in an efficient synthesis of dibenzylglycine, the α,α-disubstituted homologue of phenylalanine. It does not have its potential mirror symmetry in the crystal.
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Refinement of the title compound from 100 K CCD data yields physically reasonable anisotropic displacement parameters for the C atoms, and no anomalous endocyclic angles in the phenyl rings.
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The structure of the C-terminal dipeptide of several naturally occurring peptaibols has been determined. Crystal packing interactions via intermolecular hydrogen bonds occur only in one direction, while in the other directions, contacts are established via van der Waals interactions.
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The title compound is a versatile complexing agent for the solvent extraction of transition metal ions. The structure shows an intermolecular hydrogen bond between the imino N—H group of the ligand and a water molecule, which stabilizes the 1,3-diketone form of the molecule.
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20-Hydroxyimino-5α-pregna-9(11),16-dien-3β-yl acetate and 17-oxo-5α-androst-9(11)-en-3β-yl acetate
In both title compounds, (I) and (II), respectively, the ester linkage in ring A is equatorial. The six-membered A and B rings have chair conformations, but ring C is a half-chair. The five-membered D ring adopts a 14α-envelope conformation. The A/B, B/C and C/D ring junctions are trans.
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The structure of the title compound was determined to confirm the position of the keto group in the molecule prepared enantioselectively by a bioconversion from myo-inositol. There are two independent molecules showing similar geometry.
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The structure of the title compound comprises molecules that form dimers via N—H⋯N hydrogen-bonding interactions and then construct the overall network through N—H⋯O associations. The dihedral angle between the phenyl and thiazole rings is 42.41 (6)°.
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The structure of the title compound comprises twisted molecules that associate via N—H⋯N and N—H⋯S hydrogen-bonding interactions. The dihedral angle between the phenyl ring and the five-membered thiosemicarbazide plane is 67.56 (5)°.
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The structure of the title compound comprises essentially planar molecules which crystallize in a monoclinic lattice. C—H⋯O interactions exist to both naphthoquinone O atoms and the Cl atom.
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Tetragonal polymorphic modification of tetrakis(N,N-diethyldithiocarbamato-S,S′)tellurium(IV)
The structure of a new polymorphic modification of the title compound was investigated at room temperature. The geometry of the molecule is close to that found previously in the orthorhombic modification.
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The anions in the title compound are held together by regular hydrogen bonds from the carboxylate O atoms to the ammonium cations and water molecules, forming a three-dimensional network.
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The chiral centre with a CF3 group adopts an R configuration. This provides information on the reaction mechanism for the synthesis.
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A correlation between the position of the enol H atom and the conjugation in the title compound is indicated, together with information on the colour of the compound. Weak C—H⋯O interactions are suggested.
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In the title compound, all the atoms are close to being coplanar (r.m.s deviation 0.0098 Å) except for the imino H atoms. The molecule forms a one-dimensional chain through intermolecular N—H⋯N hydrogen bonds.
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In the title compound, the benzene rings are nearly perpendicular to each other. The hydroxy group is involved in an intramolecular O—H⋯O hydrogen bond with the acetyl O atom and the COOH group forms hydrogen-bonded dimers.
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The title compound crystallizes with two independent molecules in the asymmetric unit, with conformations that differ primarily in the orientation of the acetyl group. The two conformers form A–B-type dimers via N—H⋯N hydrogen bonds.
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The title compound adopts a folded structure, forming a symmetrical cavity with an average depth of 7.3 Å and width of 4.3 Å. The folded structure is a result of one intramolecular N—H⋯O hydrogen bond. A linear chain motif along the c axis best describes the extended intermolecular N—H⋯O hydrogen bonding.
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The title compound crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.