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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.
- ItemCrystal structure of diethyl (E)-2-[(benzofuran-2-yl)methylidene]succinate(Chester : International Union of Crystallography, 2015) Schirmer, Marie-Luis; Spannenberg, Anke; Werner, ThomasThe title compound, C17H18O5, was synthesized by a base-free catalytic Wittig reaction. The molÂecule consists of a diethyl itaconate unit, which is connected via the C=C double bond to a benzoÂfuran moiety. The benzoÂfuran ring system (r.m.s. deviation = 0.007 Ã…) forms dihedral angles of 79.58 (4) and 12.12 (10)° with the mean planes through the cis and trans ethÂoxyÂcarbonyl groups, respectively. An intraÂmolecular C-H...O hydrogen bond involving the O atom of the benzoÂfuran moiety is observed. In the crystal, molÂecules are linked into ribbons running parallel to the b axis by C-H...O hydrogen bonds.
- ItemIntermolecular hydrogen bonding in isostructural pincer complexes [OH-(t-BuPOCOPt-Bu)MCl] (M = Pd and Pt)(Chester : International Union of Crystallography, 2019) Joksch, M.; Spannenberg, A.; Beweries, T.In the crystal structure of the isostructural title compounds, namely {2,6-bis[(di-tert-butylphosphanyl)oxy]-4-hydroxyphenyl}chloridopalladium(II), [Pd(C22H39O3P2)Cl], 1, and {2,6-bis[(di-tert-butylphosphanyl)oxy]-4-hydroxyphenyl}chloridoplatinum(II), [Pt(C22H39O3P2)Cl], 2, the metal centres are coordinated in a distorted square-planar fashion by the POCOP pincer fragment and the chloride ligand. Both complexes form strong hydrogen-bonded chain structures through an interaction of the OH group in the 4-position of the aromatic POCOP backbone with the halide ligand.
- 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.
- ItemHydrolysis Stability of Bidentate Phosphites Utilized as Modifying Ligands in the Rh-Catalyzed n-Regioselective Hydroformylation of Olefins(Washington, DC : ACS, 2016) Zhang, Baoxin; Jiao, Haijun; Michalik, Dirk; Kloß, Svenja; Deter, Lisa Marie; Selent, Detlef; Spannenberg, Anke; Franke, Robert; Börner, ArminThe stability of ligands and catalysts is an almost neglected issue in homogeneous catalysis, but it is crucial for successful application of this methodology in technical scale. We have studied the effect of water on phosphites, which are the most applied cocatalysts in the n-regioselective homogeneous Rh-catalyzed hydroformylation of olefins. The stability of the bidentate nonsymmetrical diphosphite L1, as well as its two monophosphite constituents L2 and L3, toward hydrolysis was investigated by means of in situ NMR spectroscopy under similar conditions as applied in industry. Hydrolysis pathways, intermediates, and kinetics were clarified. DFT calculations were used to support the experimentally found data. The acylphosphite unit L2, which reacts with water in an unselective manner, was proven to be much less stable than the phenolphosphite L3. The stability of the bidentate ligand L1 can be therefore mainly attributed to its phenolphosphite moiety. With an excess of water, the hydrolysis of L1 and L2 as well as their Rh-complexes is first-order with respect to the phosphite. Surprisingly, coordination to Rh significantly stabilizes the monodentate ligand L2, while in strong contrast, the bidentate ligand L1 decomposes faster in the Rh complex. NMR spectroscopy provided evidence for the existence of species from decomposition of phosphites, which can likewise coordinate as ligands to the metal. Electron-withdrawing groups in the periphery of the acylphosphite moiety decrease the stability of L1, whereas 3,5-disubstituted salicylic acid derivatives with bulky groups showed superior stability. These modifications of L1 also give rise to different catalytic performances in the n-regioselective hydroformylation of n-octenes and 2-pentene, from which the 3,5-di-t-butyl-substituted ligand offered a higher n-regioselectivity accompanied by a lowering of the reaction rate in comparison to the parent ligand L1.
- ItemIron-Based Binary Catalytic System for the Valorization of CO2 into Biobased Cyclic Carbonates(Washington, DC : ACS Publ., 2016) Büttner, Hendrik; Grimmer, Christoph; Steinbauer, Johannes; Werner, ThomasThe atom economic conversion of epoxidized vegetable oils and fatty acid derivatives with CO2 into cyclic carbonates permits the synthesis of novel oleo compounds from renewable resources as well as the valorization of CO2 as a C1-building block. Organic phosphorus salts proved to be selective catalysts for this reaction. In a widespread screening 11 inexpensive and nontoxic iron salts were evaluated as cocatalysts to enhance the reaction rate. In the presence of 0.25 mol % iron chloride the selectivity and conversion were significantly improved. The reaction parameters were optimized under solvent-free conditions, and the scope and limitation were evaluated for 9 epoxidized fatty acid esters and 4 epoxidized vegetable oils. The biobased carbonates were isolated in excellent yields up to 95% and can be considered to be based on 100% CO2 in respect to carbon. This binary catalyst system features high efficiency and plain simplicity while valorizing CO2 into cyclic carbonates based on renewable feedstocks.
- ItemCrystal structure of bis{μ2-[(2-iminocyclopentylidene)methylidene]azanido-κ2 N:N'}bis[(η5-pentamethylcyclopentadienyl)zirconium(IV)] hexane monosolvate(Chester : International Union of Crystallography, 2015) Becker, Lisanne; Spannenberg, Anke; Arndt, Perdita; Rosenthal, UweThe title compound, [Zr2(C10H15)4(C6H6N2)2]·C6H14, was obtained by the stoichiometric reaction of adipoÂnitrile with [Zr(C10H15)2([eta]2-Me3SiC2SiMe3)]. IntraÂmolecular nitrile-nitrile couplings and deprotonation of the substrate produced the (1-imino-2-enimino)ÂcycloÂpentane ligand, which functions as a five-membered bridge between the two metal atoms. The ZrIV atom exhibits a distorted tetraÂhedral coordination sphere defined by two pentaÂmethylÂcycloÂpentaÂdienyl ligands, by the imino unit of one (1-imino-2-enimino)ÂcycloÂpentane and by the enimino unit of the second (1-imino-2-enimino)ÂcycloÂpentane. The cycloÂpentane ring of the ligand shows an envelope conformation. The asymmetric unit contains one half of the complex and one half of the hexane solvent molÂecule, both being completed by the application of inversion symmetry. One of the pentaÂmethylÂcycloÂpentaÂdienyl ligands is disordered over two sets of sites with a refined occupancy ratio of 0.8111 (3):0.189 (3). In the crystal, the complex molÂecules are packed into rods extending along [100], with the solvent molÂecules located in between. The rods are arranged in a distorted hexaÂgonal packing.
- ItemCrystal structure of (E)-dodec-2-enoic acid(Chester : International Union of Crystallography, 2015) Sonneck, Marcel; Peppel, Tim; Spannenberg, Anke; Wohlrab, SebastianThe crystal structure of (E)-dodec-2-enoic acid, C12H22O2, an [alpha],[beta]-unsaturated carbÂoxyÂlic acid with a melting point (295 K) near room temperature, is characterized by carbÂoxyÂlic acid inversion dimers linked by pairs of O-H...O hydrogen bonds. The carbÂoxyÂlic acid group and the following three carbon atoms of the chain of the (E)-dodec-2-enoic acid molÂecule lie almost in one plane (r.m.s. deviation for the four C atoms and two O atoms = 0.012 Ã…), whereas the remaining carbon atoms of the hydroÂcarbon chain adopt a nearly fully staggered conformation [moduli of torsion angles vary from 174.01 (13) to 179.97 (13)°].
- ItemCrystal structure of (E)-undec-2-enoic acid(Chester : International Union of Crystallography, 2015) Sonneck, Marcel; Peppel, Tim; Spannenberg, Anke; Wohlrab, SebastianIn the molÂecule of the title low-melting [alpha],[beta]-unsaturated carbÂoxyÂlic acid, C11H20O2, the least-squares mean line through the octyl chain forms an angle of 60.10 (13)° with the normal to plane of the acrylic acid fragment (r.m.s. deviation = 0.008 Ã…). In the crystal, centrosymmetrically related molÂecules are linked by pairs of O-H...O hydrogen bonds into dimers, forming layers parallel to the (041) plane.
- ItemCrystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand(Chester : International Union of Crystallography, 2016) Kessler, Monty; Godemann, Christian; Spannenberg, Anke; Beweries, TorstenThe crystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [di-methylbis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ2O,O')titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido-[di-methyl-bis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetra-hedral geometry, with the tri-fluoro-methane-sulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π-π stacking inter-actions involving the toluene solvent mol-ecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed.