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61.
62.
Walter Bauer Jochen Ellermann Martina Dotzler Diana Pohl Frank W. Heinemann Matthias Moll 《无机化学与普通化学杂志》2000,626(2):574-587
Chemistry of Polyfunctional Molecules. 133. X‐Ray Crystal Structural, Solid‐state 31P CP/MAS NMR, TOSS, 31P COSY NMR, and Mechanistic Contributions to the Co‐ordination Chemistry of Octacarbonyldicobalt with the Ligands Bis(diphenylphosphanyl)amine, Bis(diphenylphosphanyl)methane, and 1,1,1‐Tris(diphenylphosphanyl)ethane Co2(CO)8 reacts with bis(diphenylphosphanyl)amine, HN(PPh2)2 (Hdppa, 1 ), in two steps to afford the known compound [Co(CO)(Hdppa‐κ2P)2][Co(CO)4] · 2 THF ( 6 a · 2 THF). The intermediate [Co(CO)2(Hdppa‐κ2P) · (Hdppa‐κP)][Co(CO)4] · dioxane · n‐pentane ( 5 · dioxane · n‐pentane) was isolated for the first time and was characterized by X‐ray analysis. The cation 5 + exhibits a slightly distorted trigonal‐bipyramidal geometry. Detailed 31P‐NMR investigations (solid‐state CP/MAS NMR, TOSS, 31P‐COSY, 31P‐EXSY) showed that the additional tautomer [Co(CO)2(Hdppa‐κ2P)(Ph2P–N=P(H)Ph2‐κP)]+ ( 5 ′+) is present in solution. The tautomer equilibrium is slow in the NMR time scale. In contrast to the solid state only tetragonal pyramidal species of 5 are found in solution. At –90 °C there is slow exchange between the three diastereomeric species 5 a +– 5 c +. Compound 5 forms [Co(CO) · (Hdppa‐κ2P)2]BPh4 · THF ( 6 b · THF) in THF with NaBPh4 under CO‐Elimination. A X‐ray diffraction investigation shows that the cation 6 + consists of a slightly distorted trigonal‐bipyramidal co‐ordination polyeder. However, a distorted tetragonal‐pyramidal structure has been found for the cation 7 + of the related compound [Co(CO)(dppm)2][Co(CO)4] · 2 THF ( 7 · 2 THF; dppm = bis(diphenylphosphanyl)methane, Ph2PCH2PPh2). A comparison with the known [8] trigonal‐bipyramidal stereoisomer, ascertained for 7 + of the solvent‐free 7 , is described. In solutions of 6 a · 2 THF and 7 · 2 THF 13C{1H}‐ and 31P{1H}‐NMR spectra indicate an exchange of all CO and organophosphane molecules between cobalt(I) cation and cobalt(–I) anion. A concerted mechanism for the exchange process is discussed. CO elimination leads to discontinuance of the cyclic mechanism by forming binuclear substitution products such as the isolated Co2(CO)2 · (μ‐CO)2(μ‐dppm)2 · 0.83 THF ( 8 · 0.83 THF), which was characterized by spectroscopy and X‐ray analysis. For the dissolved [Co(CO)2CH3C(CH2PPh2)3][Co(CO)4] · 0.83 n‐pentane ( 9 a · 0.83 n‐pentane) no CO and triphos exchange processes between the cation and the anion are observed. Metathesis of 9 a · 0.83 n‐pentane with NaBPh4 yields [Co(CO)2CH3C(CH2PPh2)3]BPh4 ( 9 b ) which has been characterized by single‐crystal X‐ray analysis. The cation shows a small distorted tetragonal‐pyramidal structure. 相似文献
63.
64.
Martin Hofmann Dr. Christine Höhn Frank W. Heinemann Dr. Ulrich Zenneck Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(24):5998-6007
Cage chirality : Cyclic addition reactions of chirally modified stannyl‐1,2,4‐triphospholes with tBuC?P leads to stannylated P5‐deltacyclenes in high yields as separable 1:1 mixtures of diastereomers. Destannylation of a separated diastereomer gives a single enantiomer of an optically pure P? C cage compound. The novel cage‐chiral P5C4 unit (shown here) dominates the chiroptical properties, not only of the isolated enantiomer, but of the diastereomeric compounds as well.
65.
The suitability of a teicoplanin-aglycone based chiral stationary phase for the simulated moving bed (SMB) enantioseparation of amino acids under enzyme-compatible conditions was shown following a procedure that is based solely on model-based simulations and HPLC experiments. A set of eight amino acids could be separated employing aqueous solvent containing only 10% (v/v) methanol, five of them with baseline resolution. The impact of type and concentration of organic modifier and pH modifier and pH on the separation characteristics of racemic methionine was investigated. Invariant elution profiles of repetitive adsorption/desorption of large amounts of methionine representing SMB-like conditions suggest stable adsorption behavior. Competitive loading capacity (20 mg of methionine per g of chiral stationary phase (CSP)) and SMB productivity (1 g of D-methionine per g of CSP per day) were predicted. The applied transport-dispersive model based on a competitive Bi-Langmuir isotherm was validated and its parameter estimated by model-based experimental analysis. 相似文献
66.
Till Heinemann Matthias Springer Hermann Lienhart Stefan Kniesburges Carsten Othmer Stefan Becker 《Experiments in fluids》2014,55(5):1-11
Lift and drag of a passenger car are strongly influenced by the flow field around its rear end. The bluff body geometry produces a detached, transient flow which induces fluctuating forces on the body, affecting the rear axle, which may distress dynamic stability and comfort significantly. The investigations presented here deal with a 1:4 scale model of a simplified test car geometry that produces fluctuating lift and drag due to its strongly rounded rear geometry. To examine the influence of active flow control on this behavior, steady air jets were realized to exhaust from thin slots across the rear in three different configurations. Investigations were performed at $Re = 2.1 \times 10^{6}$ and included the capturing of effective integral lift and drag, velocity measurements in the surrounding flow field with Laser Doppler Anemometry, surface pressure measurements and surface oil flow visualization on the rear. The flow field was found to be dominated by two longitudinal vortices, developing from the detachment of the flow at the upper C-pillar positions, and a recirculating, transverse vortex above the rear window. With an air jet emerging from a slot across the surface right below the rear window section, tangentially directed upstream toward the roof section, total lift could be reduced by more than 7 %, with rear axle lift reduction of about 5 % and negligible drag affection ( $<$ 1 %). 相似文献
67.
Kosog B La Pierre HS Heinemann FW Liddle ST Meyer K 《Journal of the American Chemical Society》2012,134(11):5284-5289
Oxidation of our previously reported uranium(V) oxo complexes, supported by the chelating ((R)ArO)(3)tacn(3-) ligand system (R = tert-butyl (t-Bu), 1-t-Bu; R = 1-adamantyl (Ad), 1-Ad), yields terminal uranium(VI) oxo complexes [(((R)ArO)(3)tacn)U(VI)(O)]SbF(6) (R = t-Bu, 2-t-Bu; R = Ad, 2-Ad). These complexes differ in their molecular geometry in that 2-t-Bu possesses pseudo-C(s) symmetry in solution and solid state as the terminal oxo ligand lies in the equatorial plane (as defined by the three aryloxide arms of the ligand) in order to accommodate the thermodynamic preference of high-valent uranium oxo complexes to have a σ- and π-donating ligand trans to the oxo (vis-à-vis the ubiquity of the linear UO(2)(2+) moiety). The distortion of the ligand--which stands in contrast to all other complexes of uranium supported by the ((R)ArO)(3)tacn(3-) ligand, including 2-Ad--is most clearly seen in the structures of 2-t-Bu, [(((t-Bu)ArO)(3)tacn)U(VI)(O)(eq)]SbF(6), and 3-t-Bu, [(((t-Bu)ArO)(3)tacn)U(VI)(O)(eq)(OC(O)CF(3))(ax)]. The solid-state structure of 3-t-Bu reveals that the trans U-O(ArO) bond length is shortened by 0.1 ? in comparison to the cis U-O(ArO) bonds and the trans U-O-C(ipso) angle is linearized (157.67° versus 147.85° and 130.03°). Remarkably, the minor modification of the ligand to have Ad groups at the ortho positions of the aryloxide arms is sufficient to stabilize a C(3v)-symmetric terminal uranium(VI) oxo complex (2-Ad) without a ligand trans to the oxo. These experimental results were reproduced in DFT calculations and allow the qualitative bracketing of the relative thermodynamic stabilization afforded by the inverse trans-influence as ~6 kcal mol(-1). 相似文献
68.
AC Schmidt AV Nizovtsev A Scheurer FW Heinemann K Meyer 《Chemical communications (Cambridge, England)》2012,48(69):8634-8636
The new neopentyl (Neop)-substituted tris(aryloxide) U(iii) complex [(((Neop,Me)ArO)(3)tacn)U(III)] reacts with CO(2) to form CO and the bridging carbonate complex [{(((Neop,Me)ArO)(3)tacn)U(IV)}(2)(μ-CO(3))]. The uranium(iv) bridging oxo [{(((Neop,Me)ArO)(3)tacn)U(IV)}(2)(μ-O)] has been determined to be the intermediate in this reaction. For the first time, both U(iv) complexes can be reduced back to the U(iii) starting material. Thus, with KC(8) as reductant, [(((Neop,Me)ArO)(3)tacn)U(III)] engages in a synthetic cycle, in which CO(2) is converted to CO and CO(3)(2-). 相似文献
69.
Dielectric measurements on oriented liquid crystalline substances in the frequency range from 10 Hz to 100 kHz have been carried out. The static dielectric constant parallel to the director of both single components shows a strong decrease in relation to the expected value. In the case of the swallow-tailed compound this effect can be described by assuming an equilibrium between statistically and antiparallel oriented molecules. The second component has an extremly strong tendency to be antiparallel oriented. In the mixture of both a continuous change of the correlation was observed. 相似文献
70.
The use of the pyN4 coordination cap to synthesize high‐nuclearity clusters supported by polycyanometallate units was explored. The heptanuclear bimetallic complexes 2 and 3 were obtained as their salts by reacting stoichiometric amounts of pyN4 and Ni(ac)2 with K3[Fe(CN)6] and K4[Mo(CN)8], respectively. The tetranuclear complex 4 formed as a by‐product in the synthesis of 3 . Temperature‐dependent magnetic susceptibility measurements carried out for 2 revealed that this compound behaves as a paramagnet over the whole range of temperatures. 相似文献