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- Item2-hydroxyethylammonium iodide(Chester : International Union of Crystallography, 2014) Kohrt, C.; Spannenberg, A.; Werner, T.In the crystal structure of the title salt, C2H 8NO+·I-, N-H⋯O, N-H⋯I and O-H⋯I hydrogen bonds lead to the formation of layers staggered along the c axis.
- Item(Cyanido-κC)(2,2-diphenylacetamido-κ2 N,O)bis(η5-pentamethylcyclopentadienyl)zirconium(IV)(Chester : International Union of Crystallography, 2014) Becker, L.; Spannenberg, A.; Arndt, P.; Rosenthal, U.In the title compound, [Zr(C10H15)2(C14H12NO)(CN)], the ZrIV atom is coordinated by two pentamethylcyclopentadienyl ligands, the amidate ligand via the N and O atoms, and an additional C N ligand. The four-membered metallacycle is nearly planar (r.m.s. deviation = 0.008Å). In the crystal, the molecules are connected into centrosymmetric dimers via pairs of N - HN hydrogen bonds.
- Item(η6-Benzene)(carbonato-κ2O,O') [dicyclohexyl(naphthalen-1-ylmethyl)phosphanejP] ruthenium(II) chloroform trisolvate(Chester : International Union of Crystallography, 2014) Gowrisankar, S.; Neumann, H.; Spannenberg, A.; Beller, M.The title compound, [Ru(CO3)(η6-C 6H6){(C6H11)2P(CH 2-C10H7)}]-3CHCl3, was synthesized by carbonation of [RuCl2-(η6-C6H 6){(C6H11)2P(CH2C 10H7)}] with NaHCO3in methanol at room temperature. The RuIIatom is surrounded by a benzene ligand, a chelating carbonate group and a phosphane ligand in a piano-stool configuration. The crystal packing is consolidated by C-H⋯O and C-H⋯Cl hydrogen-bonding interactions between adjacent metal complexes and between the complexes and the solvent molecules. The asymmetric unit contains one metal complex and three chloroform solvent molecules of which only one was modelled. The estimated diffraction contributions of the other two strongly disordered chloroform solvent molecules were substracted from the observed diffraction data using the SQUEEZE procedure in PLATON.
- ItemBis(μ2-isopropylimido-κ2 N:N)bis[(η5-cyclopentadienyl)(ethenolato-κO)titanium(IV)](Chester : International Union of Crystallography, 2014) Haehnel, M.; Spannenberg, A.; Rosenthal, U.The title dinuclear half-sandwich complex, [CpTi(OCH=CH2) (μ2-N-iPr)]2 (Cp = cyclopentadienyl; iPr = isopropyl), was obtained from the reaction of Cp2TiCl2, n-butyllithium and isopropylamine in tetrahydrofuran. Each TiIV atom is coordinated by one Cp ligand, one vinyloxy unit and two bridging imido groups in a strongly distorted tetrahedral geometry. There are two half molecules in the asymmetric unit, such that whole molecules being generated by inversion symmetry.
- Item(η6-Benzene)dichlorido(chlorodicyclohexylphosphane-κp) ruthenium(II) chloroform monosolvate(Chester : International Union of Crystallography, 2014) Gowrisankar, S.; Neumann, H.; Spannenberg, A.; Beller, M.The title compound, [RuN4(-6-C6H6) (C12H22ClP)]-CHCl3, was prepared by reaction of [RuN 4(-6-C6H6)]2 with chlorodicyclohexyl phosphane in CHCl3 at 323 K under argon. The RuII atom is surrounded by one arene ligand, two Cl atoms and a phosphane ligand in a piano-stool geometry. The phosphane ligand is linked by the P atom, with an Ru-P bond length of 2.3247 (4) Å. Both cyclohexyl rings at the P atom adopt a chair conformation. In the crystal, the RuII complex molecule and the chloroform solvent molecule are linked by a bifurcated C-H⋯(Cl,Cl) hydrogen bond. Intramolecular C-H⋯Cl hydrogen bonds are also observed.
- ItemThe effect of supported MoOX structures on the reaction pathways of propene formation in the metathesis of ethylene and 2-butene(Cambridge : RSC, 2014) Hahn, T.; Kondratenko, E.V.; Linke, D.The kind of surface MoOX structures on Al2O3–SiO2 was found to determine propene selectivity in the metathesis of ethylene and 2-butene. Compared to isolated tetrahedral MoOX species, their polymerized octahedral counterparts show significantly lower activity for isomerisation of 2- to 1-butene thus hindering non-selective metathesis of these butenes. In addition, they reveal higher ability to engage ethylene in propene formation.
- ItemDetermining surface structure and stability of ε-Fe2C, χ-Fe5C2, θ-Fe3C and Fe4C phases under carburization environment from combined DFT and atomistic thermodynamic studies(London : Taylor & Francis, 2014) Zhao, Shu; Liu, Xing-Wu; Huo, Chun-Fang; Li, Yong-Wang; Wang, Jianguo; Jiao, HaijunThe chemical–physical environment around iron based FTS catalysts under working conditions is used to estimate the influences of carbon containing gases on the surface structures and stability of ε-Fe2C, χ-Fe5C2, θ-Fe3C and Fe4C from combined density functional theory and atomistic–thermodynamic studies. Higher carbon content gas has higher carburization ability; while higher temperature and lower pressure as well as higher H2/CO ratio can suppress carburization ability. Under wide ranging gas environment, ε-Fe2C, χ-Fe5C2 and θ-Fe3C have different morphologies, and the most stable non-stoichiometric termination changes from carbon-poor to carbon-rich (varying surface Fe/C ratio) upon the increase in ΔμC. The most stable surfaces of these carbides have similar surface bonding pattern, and their surface properties are related to some common phenomena of iron based catalysts. For these facets, χ-Fe5C2-(100)-2.25 is most favored for CO adsorption and CH4 formation, followed by θ-Fe3C-(010)-2.33, ε-Fe2C-(121)-2.00 and Fe4C-(100)-3.00, in line with surface work function and the charge of the surface carbon atoms.
- ItemAlZn based Co and Ni catalysts for the partial oxidation of bioethanol - Influence of different synthesis procedures(Warsaw : Central European Science Journals, 2014) Ehrich, H.; Kraleva, E.The catalytic performance of Co and Ni catalysts on AlZn mixed oxide supports depends on the synthesis procedure used for their preparation. For this study CoAlZn and NiAlZn catalysts were prepared by conventional sol-gel synthesis of the mixed oxide and subsequent impregnation of the support with the transition metal (SG = sol gel method) as well as by a single-step method were a gel is formed based on salts of all components using citric acid as chelating agent (CM = citrate method). The structure and morphology of the catalysts were characterized by nitrogen sorption, XRD and TPR measurements. They showed high activity in the partial oxidation of ethanol at 600-750 °C, but their properties depend on the preparation method. The higher performance of the catalysts prepared by the citrate method, where the transition metal is incorporated into the crystal structure of the support during preparation, is based on a change in morphology and structure, resulting in more active sites exposed on the surface. Compared to the Co catalysts, Ni catalysts showed a higher performance. This might be due to the higher reducibility and the smaller Ni particles size, which allows a better interaction with the support in NiAlZn catalysts.
- ItemProbing the second dehydrogenation step in ammonia-borane dehydrocoupling: characterization and reactivity of the key intermediate, B-(cyclotriborazanyl)amine-borane(Cambridge : RSC, 2014) Kalviri, Hassan A.; Gärtner, Felix; Ye, Gang; Korobkov, Ilia; Baker, R. TomWhile thermolysis of ammonia-borane (AB) affords a mixture of aminoborane- and iminoborane oligomers, the most selective metal-based catalysts afford exclusively cyclic iminoborane trimer (borazine) and its B–N cross-linked oligomers (polyborazylene). This catalysed dehydrogenation sequence proceeds through a branched cyclic aminoborane oligomer assigned previously as trimeric B-(cyclodiborazanyl)amine-borane (BCDB). Herein we utilize multinuclear NMR spectroscopy and X-ray crystallography to show instead that this key intermediate is actually tetrameric B-(cyclotriborazanyl)amine-borane (BCTB) and a method is presented for its selective synthesis from AB. The reactivity of BCTB upon thermal treatment as well as catalytic dehydrogenation is studied and discussed with regard to facilitating the second dehydrogenation step in AB dehydrocoupling.
- ItemProbing molecular interaction in ionic liquids by low frequency spectroscopy: Coulomb energy, hydrogen bonding and dispersion forces(London [u.a.] : Royal Society of Chemistry, 2014) Fumino, K.; Reimann, S.; Ludwig, R.Ionic liquids are defined as salts composed solely of ions with melting points below 100 °C. These remarkable liquids have unique and fascinating properties and offer new opportunities for science and technology. New combinations of ions provide changing physical properties and thus novel potential applications for this class of liquid materials. To a large extent, the structure and properties of ionic liquids are determined by the intermolecular interaction between anions and cations. In this perspective we show that far infrared and terahertz spectroscopy are suitable methods for studying the cation-anion interaction in these Coulomb fluids. The interpretation of the measured low frequency spectra is supported by density functional theory calculations and molecular dynamics simulations. We present results for selected aprotic and protic ionic liquids and their mixtures with molecular solvents. In particular, we focus on the strength and type of intermolecular interaction and how both parameters are influenced by the character of the ions and their combinations. We show that the total interaction between cations and anions is a result of a subtle balance between Coulomb forces, hydrogen bonds and dispersion forces. For protic ionic liquids we could measure distinct vibrational modes in the low frequency spectra indicating clearly the cation-anion interaction characterized by linear and medium to strong hydrogen bonds. Using isotopic substitution we have been able to dissect frequency shifts related to pure interaction strength between cations and anions and to different reduced masses only. In this context we also show how these different types of interaction may influence the physical properties of ionic liquids such as the melting point, viscosity or enthalpy of vaporization. Furthermore we demonstrate that low frequency spectroscopy can also be used for studying ion speciation. Low vibrational features can be assigned to contact ion pairs and solvent separated ion pairs. In conclusion we showed how detailed knowledge of the low frequency spectra can be used to understand the change in interaction strength and structure by variation of temperature, solvent polarity and solvent concentration in ionic liquids and their mixtures with molecular solvents. In principle the used combination of methods is suitable for studying intermolecular interaction in pure molecular liquids and their solutions including additive materials such as nanoparticles.