November 2000 issue
Precise X-ray and neutron structural determinations of Na2Fe(CN)5(NO)·2D2O performed at very low temperatures are presented. The X-ray and neutron diffraction positional and atomic displacement parameters agree very well. The [Fe(CN)5(NO)]2− anion has approximate octahedral stereochemistry.
In the title compound, octahedrally coordinated vanadium and tetrahedral sulfate ions share corners to form layers that are held together by hydrogen bonds and by sodium ions, which are located between the layers.
electronic papers (metal-organic compounds)
The cation of the title compound displays a rhomboidal geometry for the Au atoms, with short Au⋯Au distances of 3.104 (2) and 3.185 (1) Å. The anion shows the expected square-planar geometry at AuIII, with the Au atom 0.022 (5) Å out of the plane of the four donor atoms.
In the title complex, the Cu atom, which is located on an inversion centre, is in the centre of a distorted octahedral geometry, with six O atoms provided by two monodentate carboxylate groups and four water molecules. Intra- and intermolecular hydrogen bonds make up a three-dimensional network.
The previously reported title compound (R = 0.12, one of water molecules disordered) has been redetermined (R = 0.041, no disorder). The complex has pseudo-octahedral geometry around the FeIII atom. There is extensive hydrogen bonding involving the water molecules and the hydroxamate ligands.
The title compound, prepared in the course of synthetic studies of organochalcogenide compounds of PdII, has bridging chloro and arylthiolato groups, with the phosphines being trans to the bridging chloro group. The four-membered metallocyclic Pd2ClS ring is unexpectedly non-planar, with a dihedral angle of 133.8 (1)° between the PdCl2SP coordination planes.
The preparation and crystal structure of the title complex are described. The ZnII ion adopts a distorted tetrahedral coordination. It is bonded to two thiocyanate and two pyridyl N atoms.
The structure of the title compound is the first example of an addition compound of GeCl4 with two aromatic nitrogen bases. The environment around the Ge atom can be described as a slightly distorted octahedron with the 4-methylpyridine ligands occupying axial positions and the four chloro ligands in the equatorial plane. The structure of the title compound is isomorphous with the corresponding silicon halides.
The reactions of GeBr4 with 4-methylpyridine and 3,4-dimethylpyridine lead to tetrabromobis(4-methylpyridine)germanium, (I
>), and tetrabromobis(3,4-dimethylpyridine)germanium, (II >), respectively. These structures show the same features as the corresponding silicon complexes.
The title copper complex has a center of symmetry and a distorted octahedral coordination, with four N atoms in equatorial positions and water molecules in the apical sites. The water molecule of crystallization is hydrogen bonded to the deprotonated carboxylate group of the ligand.
The title compound is a new open-framework zinc arsenate, which is isostructural with the zinc phosphate UiO-17. The open three-dimensional anionic framework, made up of vertex-sharing AsO4 tetrahedra, ZnO4 tetrahedra and ZnO5 trigonal bipyramids, contains a two-dimensional eight-ring channel system in which diprotonated piperazinium cations reside.
The title compound crystallizes as a monomer, with the copper ion in a pentacoordinated square-pyramidal environment, bisected by a twofold axis passing through the metal atom and the apex. The molecules organise in chains connected by hydrogen bonds running along the unique b axis.
electronic papers (organic compounds)
In the two title adducts, (I
>) and (II >), respectively, the dicarboxylic acid is connected to two cinnamamide molecules through cyclic hydrogen bonds. The arrangement of the C=C bonds of neighbouring cinnamamide molecules is twisted.
In the title adduct, a hydrogen-bonded unit of the acid and two cinnamamide molecules has a crystallographic twofold axis parallel to b, and the acid molecules are linked by cyclic hydrogen bonds to form a flat zigzag along c.
In the title compound, the tosyloxymethyl substituent is in an endo position; the BH3 group is equatorial and the (N-bonded) methyl group is axial, relative to the six-membered heterocycle. The N—B bond of 1.649 (8) Å is one of the longest known.
The three title sterically encumbered terphenyl halides are isomorphous and isostructural with a plane of symmetry through the centre of the molecule. The C—X bond distances are 1.745 (3) [X = Cl, (I)], 1.910 (4) [X = Br, (II)] and 2.102 (6) Å [X = I, (III)].
The 5-fluoropyrimidine-2,4(1H,3H)-dione moiety of the title compound