November 1999 issue
cif-access (inorganic compounds)
The structure of Na2Zn(OH)PO4 [Kabalov, Simonov & Belov (1972). Dokl. Akad. Nauk SSSR, 202, 823-826] has been redetermined and the hydrogen-bonding geometry elucidated. The tetrahedral ZnO4 and PO4 geometrical parameters are normal [dav(Zn—O) = 1.953 (17) Å and dav(P—O) = 1.54 (2) Å].
cif-access (metal-organic compounds)
The octahedral [TiCl4(dme)] complex (dme is 1,2-dimethoxyethane) has C2 molecular symmetry and is isostructural with its rhenium and molybdenum analogues.
The title compound, whose aqua ligand is exceedingly labile, crystallizes in a monoclinic form without a solvent molecule of crystallization. A recently observed triclinic form of this complex crystallized as a monohydrate. The Mn—O distance [2.102(3)Å] is consistent with the bond distance reported for the triclinic form [2.075(2)Å] and the related complex [(depe)(CO)3Mn(OH2)]BF4 [2.115(2)Å; depe is 1,2-bis(diethylphosphino)ethane].
The dihedral angles between the phenyl rings and the dionate chelate atoms of the associated six-membered manganese-containing rings are 19.03(15) and 21.08(13)°.
cif-access (organic compounds)
Both title compounds, 1,5-diphenylpentane-2,4-dione, (1), and 1,5-bis(2-naphthyl)pentane-2,4-dione, (2), exist in the enol form and have a planar enol ring with a short crystallographically symmetric hydrogen bond. In addition, the molecules possess twofold rotation symmetry so that the ketone and enol functionalities are completely delocalized.
The title compound adopts a chair–chair conformation in the solid state. It does not have effective mirror symmetry because the H atom of the hydroxy group lies markedly out of the mean plane of the central OC2PS unit.
The title compound was found to exist solely as its ap rotamer in both the crystalline form and in solution, the exhibited structural distortions being reflected in the observed rotational hindrance. The more sterically restricted 9-(o-tert-butylphenyl)-9-fluorenol exists solely as its sp rotamer under these conditions.
The centrosymmetry of the title compound results in parallelism of the phenyl as well as the fluorene planes. The phenyl planes are nearly perpendicular to their respective fluorene planes and each isopropyl group almost impinges on its fluorene plane, imposing substantial angular distortion.
The title structure was determined at 153K to establish the absolute configuration of the chiral centers. The N atom of the pyrrolizidine group is pyramidal. Both five-membered rings have approximate twist conformations, with pseudo-twofold axes passing through the N atom. The crystal packing shows intermolecular O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds.
The B atom in the title compound is chelated by the 1,3-diphenylpropene-1,3-dionate [B—O 1.363(3) and 1.370(3)Å] and naphthalene-2,3-diolate [B—O 1.298(3) and 1.309(3)Å] groups; the two chelate rings are orthogonal to one another [dihedral nobreak angle 89.9(1)Å].
The title compound is a polymorph (Z = 2, space group P1) of the orthorhombic form reported by Toda, Tanaka, Miyamoto, Koshima, Miyahara & Hirotsu [J. Chem. Soc. Perkin Trans. 2 (1997), pp. 1877–1885]. There is an intramolecular O—H⋯O hydrogen bond in each molecule, with the second hydroxy group free and not participating in hydrogen bonding.
The title molecule is approximately planar, with the nitro group strongly conjugated with the π-system. Ab initio calculations indicate that the distortion of the exo angles of the cyclic C(Ar)—C(=O)—O fragment arises from intramolecular rather than intermolecular effects.
The title compound consists of parallel infinite chains of trans-corner-connected TiF6 octahedra along the b axis, separated from each other by NH4+ ions.
The structure of the title compound features In atoms in a distorted fac-octahedral geometry and involves a three-dimensional network of intermolecular hydrogen bonding. It is the first structurally characterized example of a discrete trihydrate of a Group 13 MIII halide (M = B, Al, Ga or In).
The structure of CaBa2(HPO4)2(H2PO4)2 consists of infinite [Ca(HPO4)2(H2PO4)2] anionic chains, built up from CaO6, HPO4 and H2PO4 polyhedra linked via Ca—O—P bonds. These chains are held together by nine-coordinate Ba2+ cations. A two-dimensional network of hydrogen bonds contributes to the linkage of these chains.
The structure of yttrium sodium oxalate tetrahydrate consists of corrugated layers of ninefold-coordinated Y atoms linked together by oxalate groups. Na atoms and water molecules are intercalated between the layers.