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  • 1
    Electronic Resource
    Electronic Resource
    Synthese und Eigenschaften von 1,2,4,3-Thiadiazaboretidinen. Kristallstruktur des 2,4-Di-tert-butyl-3-phenyl-1,2,4,3-thiadiazaboretidins (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 47-50 
    Details
    ISSN: 0009-2940
    Keywords: Sulfur diimides ; 1,3-Cycloaddition, reductive ; 1,2,4,3-Thiadiazaboretidines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Properties of 1,2,4,3-Thiadiazaboretidines. Crystal Structure of 2,4-Di-tert-butyl-3-phenyl-1,2,4,3-thiadiazaboretidineReaction of sulfur diimides with alkyl(aryl)bis(methylthio)boranes leads to reductive 1,3-cycloaddition of the NSN sequence with formation of the 1,2,4,3-thiadiazaboretidines 2a-g. NMR (1H, 11B, 13C, 15N, 29Si), mass spectra and the results of the X-ray analysis of 21 are reported and discussed. The 11B chemical shifts have been calculated for 3-phenyl-1,2,4,3-thiadiazaboretidine and some related model compounds by the IGLO method and correlate acceptably with the experimental values.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240108
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  • 2
    Electronic Resource
    Electronic Resource
    Decaethyl-2,6,8,10-tetracarba-nido-decaboran(10) - Herstellung, Struktur im festen Zustand und Stabilität(1) (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2715-2724 
    Details
    ISSN: 0009-2940
    Keywords: Carbaborane, nido-C4B6, organosubstituted ; Carbaborates, fusion of C2B3, C4B6 dianion ; Carbaborane, C4B6, structure, phase transformations ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decaethyl-2,6,8,10-tetracarba-nido-decaborane(10) - Preparation, Structure in the Solid State, and Stability[1]The title compound 6, prepared in two steps from the pentaethyl-1,5-dicarba-closo-pentaborane(5) (1), is characterized at 103 K as the low-temperature solid phase LT-6 by a single-crystal X-ray structure analysis; 6 reacts with alkali metals (K, Cs) to form the C4B6Et10 dianion (62-) which is easily oxidized to 6 (e.g. with I2, FeCl2, HgCl2). Ab initio MO and IGLO calculations of compound 6 have been carried out.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911241212
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  • 3
    Electronic Resource
    Electronic Resource
    Chromophore Systeme, 1. Konformation und Lichtabsorption von Hexa-1,5-dien-3,4-dion (Divinylglyoxal) (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 821-826 
    Details
    ISSN: 0009-2940
    Keywords: α-Diketones, unsaturated ; Conformers, stable ; UV-Vis transition energies ; PE Spectroscopy ; 13C-NMR chemical shifts, correlation with dihedral angles CO/CO ; Calculations, STO-3G, MMP1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chromophoric Systems, 1.  -  Conformation and Absorption of Light in Hexa-1,5-diene-3,4-dione (Divinylglyoxal)Divinylglyoxal (1) is investigated by several spectroscopic and theoretical methods in order to set up a correlation between the CO/CO dihedral angle and the transition energies in unsaturated α-diketones. According to the experimental (UV, IR, 13C-NMR, PE spectroscopy and dipole moment) and theoretical (ab initio and molecular mechanics) results, 1 exists predominantly as a C2h conformer (Θco/co=180°, ΘVinyl/co=0°). The dependence of transition energies on CO/CO dihedral angles is similar in shape to that for saturated α-diketones, but is significantly shifted to lower transition energies. 13C chemical shifts respond sensitively to CO/CO dihedral angles, and the ab initio calculated curve is supported by a few experimental results.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240423
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  • 4
    Electronic Resource
    Electronic Resource
    The Molecular Structures and Conformations of Bis(dichlorosilyl)amine and Bis(dichlorosilyl)methylamine in the Gas Phase: Determination by Electron Diffraction and by ab Initio Calculations (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 807-815 
    Details
    ISSN: 0009-2940
    Keywords: Amines, bis(dichlorosilyl) ; bis(dichlorosilyl)methyl- ; Gas-phase electron diffraction ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase molecular structures of bis(dichlorosilyl)-amine, (HSiCl22NH, and bis(dichlorosilyl)methylamine, (SiHCl2)2NMe, have been investigated by electron diffraction and ab initio calculations on a MP2/6-31G* level. Because the latter suggest the presence of a mixture of two conformers for each molecule, attempts were made to fit the electron diffraction data in each case by two different models, one assuming the presence of only one conformation, and another allowing for two different conformers. The principal parameters (ra) from electron diffraction for (HSiCl2)2NH are (the appropriate ab initio calculated values are given in brackets []): r(Si-N) 171.9(2) [172.7], r(Si-Cl) 204.1(1)[204.5] pm; Si-N-Si 126.5(8) [127.4] N-Si-Cl 107.3(5) [110.8] and Cl-Si-Cl 106.5(3) [107.5]°. For (SiHCl2)2NMe: r(Si-N) 171.1(3) [171.5], r(Si-Cl) 204.0(9) [205.2], r(N-C) 149.7(10) [148.3] pm; Si-N-Si 124.9(13) [123.4], N-Si-Cl 109.7(5) [110.7] and Cl-Si-Cl 107.1(3) [107.2]° [110.8] and Cl-Si-Cl 106.5(3) [107.5]°. For (SiHCl2)2NMe: r(Si-N) 171.1(3) [171.5], r(Si-Cl) 204.0(9) [205.2], r(N-C) 149.7(10) [148.3] pm; Si-N-Si 124.9(13) [123.4], N-Si-Cl 109.7(5) [110.7] and Cl-Si-Cl 107.1(3) [107.2]°. For (HSiCl2)2NH three different conformers were found to fit the experimental data with the single-conformation model. In two of the conformers, the dichlorosilyl groups are twisted by Θ1 = 146.0(10)/Θ2 = 155.2(20)° and Θ1= 101.1(49)/Θ2 = 196.8(12)°; respectively counterclockwise from the positions in which the Si-H bonds eclipse the N-H bond. Both of these lead to nearly ideally staggered conformations of the two SiHCl2 groups when viewed along the Si-Si axis. In contrast, the third conformation is nearly eclipsed, with torsion angles Θ1 = 131.4(15)/Θ2 = 80.4(26)°. Planarity of the Si2NH group was assumed as suggested by ab initio calculation. For (HSiCl2)2NMe the experimental data could be suitably fitted by two conformers, in which the dichlorosilyl groups are twisted by Θ1= 161.8(13)/Θ2 = 63.1(23)° and Θ1 = 156.1(9)/ Θ2 = 177.1(15)° from the positions in which the Si-H bonls eclipse the N-C bond. The first of these structures has an eclipsed Si(NSi)Cl conformation and an Si…Cl nonbonded distance close to distance clse to the sum of the appropriate van der waals radii. MP2/6-31G* calculations support the GED bond lengths and bond angles of both molecules, but indicate different conformations for the most stable equilibrium geometries: the computed twists are Θ1 = 180/Θ2 = 180° and Θ1 = 177.0/ Θ2 = 183.0° for (HSiCl2)2NH and (HSiCl2)2NMe, respectively. Rotation about the Si - N bonds is a very facile process, cf. the computed [MP2/6-31G*//MP2/6-31G* + ZPE(SCF/6-31G*)] rotational barrier of 2.9 kJ. mol-1 for (HSiCl2)2NH.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280812
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