Gezina Beurskens

Crystal and molecular structure of tetrapyridyl-copper(II)-bis-nitrato-bis-pyridine

The crystal and molecular structure of a pyridine complex of anhydrous copper(II)nitrate is described. The structure has been solved by vector search methods and refined by least-squares methods to R1=0.049 [I>2σ(I)]. The complex lies on a twofold axis parallel toa, and two solvent pyridine molecules lie on twofold axes parallel toc. The copper atom is coordinated by four pyridyl groups and two monodentate NO3 groups. Crystal data: C30H30N8O6Cu, orthorhombic, space group Pnna(52),a=14.446(7),b=12.154(5),c=16.881(4) Å,V=2964(2) Å3,Z=4.

Synthesis and X-ray structure of a novel concave tetradentate sulphur ligand system: electrochemical characterisation of a semi-encapsulated [4Fe–4S]2+ cluster complex

An Fe4S4-cluster, partly encapsulated by a concave, tetradentate ligand, mimics certain electrochemical properties of metalloproteins.

Copper(II) bipyridine and crown ether-bipyridine complexes: X-ray structures, characterization, and properties as histamine receptors

Abstract he synthesis and characterization, including the crystal structure, of the complex (2) of Cu(II) with the crown-ether bipyridine ligand, 1[5–2,2′-bipyridyl)carbonyl]-1-aza-4,7,10,13-tetraoxacyclopentadecane (1), are described. Compound 2, C27H49N3O18Cl2Cu, crystallizes in the triclinic space group P1 with cell constants a = 10.160(1), b = 13.014(1), c = 15.934(2) A, α = 74.18(1)°, β = 84.83(1)°, γ = 71.54(1)°, V = 1923.0(4) A3, Z = 2, dcalc = 1.448 g cm−3. The crystal structure was solved by vector search methods and refined by full-matrix least-squares on F2 to R = 0.086 for 3163 observed reflections (I > 2σ(I)), 83 restraints and 390 parameters. The crystals contain two formula units per cell as a dimer, with each carbonyl oxygen of one monomer complex coordinating to the copper ion of the other. Each copper has elongated octahedral coordination geometry, with two nitrogens of one bipyridyl unit and four oxygens, viz. two water molecules, one perchlorate, and one carbonyl, as ligand donor atoms...

Crystal and Molecular-Structure of Dihydro-8(B),8(C)-Diphenyl-1h,3h,4h,5h,7h,8h,-2,6-Dioxa-3a,4a,7a,8a-Tetr Aazacyclopenta[Def]Fluorene-4,8-Dithione

The title compound C20H18N4O2S2 crystallizes in the monoclinic space group P21/n witha=8.4930(1) Å,b=11.4880(1) Å,c=20.0709(2) Å, β=94.933(1)°,V=1951.01(3) Å3,Z=4. The crystal structure has been solved by vector search methods and refined by fullmatrix least-squares toR=0.04 for 2888 reflections and 116 restraints. The title compound has a suitable geometry for synthesizing receptor molecules with a cleft for selective complexation.

Menthol mediated optical resolution of 10-oxatricyclodecadienones. Application in the enantioselective synthesis of cyclopentenoids

Abstract The efficient conversion of 5-ethoxy-4-p-tolylsulphonylmhetyl-exo-10-oxatricyclo[5.2.1.02,6]deca-4,8-dien-3-one 6 into a diastereomeric mixture of the (-)menthyl ethers, 9a and 9b, is described. Separation of these ethers, followed by reduction with DIBAL and trans-etherification with NaOMe affords the enantio-merically pure methoxymethyl substituted 10-oxatricyclodecadienones (+)14 and (-)14. These tricyclodeca-dienones are enantiospecifically converted into the cyclopentadienone epoxides (-)16 and (+)16, respectively, by successive alkaline epoxidation and Flash Vacuum Thermolysis. The absolute configurations of all compounds, from 9a, 9b up to (-)16, (+)16 were established by means of X-Ray diffraction analyses.

The reliability index R2 as a versatile tool in structure analysis of inorganic and small molecular compounds

Applications of R_2 in small-molecule crystallography are described. Ways of using R_2 to evaluate initial models of a structure are discussed. These models, obtained from Patterson methods, are usually small. They may include one or more heavy atoms and pseudosymmetry is sometimes present in the model. The R_2 criterion is used also to identify misplaced atoms prior to the start of the expansion process. Finally, R_2 is used during structure expansion by the application of phase refinement or Fourier methods. Details of the procedures of extension, as well as the role of R_2 therein, are presented and evaluated. Results obtained with various test structures are discussed.

Crystal and molecular structure of heptacyclo[9,6,1,1(4,7),1(14,17),0(2,10),0(3,8),0(1,13)]-eicosa-3(8),5,1 2,15-tetrene-9,18-dione

The title compound C20H16O2 crystallizes in the monoclinic space group P 21 witha=6.0310(5)Å,b=13.9396(6)Å,c=8.5560(5)Å, β=100.354(8)°,V=770.60(8)Å3, andZ=2. The crystal structure has been solved by vector-search methods and refined by fullmatrix least-squares toR=0.05 for 4788 reflections (1>2σ(1)). The title compound has been prepared in the course of a study on cyclopentanoid natural products.

Crystal and Molecular-Structure of (2r,3r)-2-Exo-((1r)-1-Hydroxy-2-Methyl-Propyl)-3-Exo-Hydroxymethyl-Bicyc Lo[2.2.1]-Hept-5-Ene, C12h20o2

The stereogeometry of the title compound which was prepared by a stereoselective addition reaction, has been proved by an X-ray diffraction analysis. Crystal data: monoclinic, P21,a=10.495(16),b=8.392(16),c=13.209(20) Å, β=93.80(8),Z=4. The crystal structure has been solved by vector search methods and refined toR=0.05 for 782 observed reflections.