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  • crystal structure  (3)
  • Molecular structures  (2)
  • 1995-1999  (5)
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  • 1995-1999  (5)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Structural Aspects of Cyclopropyl Homoconjugation: Experimental Studies and Ab Initio Calculations (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1429-1435 
    Details
    ISSN: 0947-3440
    Keywords: Cyclopropyl homoconjugation ; Molecular structures ; Electron density determinations ; Ab initio calculations ; Spiro compounds ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low-temperature crystal structural studies of a series of saturated and unsaturated bicyclo[2.2.1]heptadiene, heptene and heptane compounds with 7-spirocyclopropyl substitution reveal significant differences in the bond lengths of the three-membered rings and in the C—C single bonds of the bicyclic fragment. A complex interplay of strain and different types of conjugation influence the molecular structure of the bicycloheptadiene derivative 1, where the difference in the length of the three-membered ring bonds is 0.040 Å and all C—C single bonds in the bicyclic fragment are lengthened significantly. Ab initio calculations at the HF/6-31G(d) (to a minor extent) and MP2/6-31G(d) levels are in good agreement with the experimental data. Calculated charge distributions and dipole moments further support the relevance of cyclopropyl homoconjugation in the investigated prototype of Walsh and through-space π-orbital interaction. Static difference electron density maps have been derived from the experimental data by multipole refinements which showed exocyclic shifts of electron density in the planes of the three-membered rings and significant bond ellipticities at the C—C single bonds in the unsaturated bicyclic units.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970721
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  • 2
    Electronic Resource
    Electronic Resource
    Structural Aspects of Cyclopropyl Conjugation: Experimental Studies and Ab Initio Calculations (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2047-2053 
    Details
    ISSN: 0947-3440
    Keywords: Conjugation ; X-ray diffraction ; Molecular structures ; Ab initio calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low temperature crystal structural studies of small cyclopropyl-conjugated unsaturated hydrocarbons reveal significant differences in bond lengths between carbon atoms mainly within the three-membered rings but also for adjacent C—C single bonds. The strongest influence of conjugation was observed for spiro[2.4]hepta-4,6-diene (1), where the difference in the lengths of three-membered ring bonds is 0.050 Å (X-ray). The same effect is also obvious from ab initio calculations at HF/6-31G(d) (to a minor extent) and MP2/6-31G(d) levels, as shown by a difference analysis of bond lengths which was performed in order to cancel out systematic errors and differences for both methods. Static difference electron density maps were derived from the experimental data by multipole refinements. These maps showed shifts of electron density to exocyclic locations within the planes of the three-membered rings and significant bond ellipticities for the adjacent single bonds. For 1,1-diethenylcyclopropane (4) a nonsymmetric conformation was found in the crystal lattice, very close to the global minimum structure calculated by ab initio methods.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971007
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  • 3
    Electronic Resource
    Electronic Resource
    Hexabromotricyclobutabenzene and Hexabromohexaradialene: Their Nickel-Mediated One-Pot Syntheses and Crystal Structure (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 208-210 
    Details
    ISSN: 0947-6539
    Keywords: crystal structure ; cyclobutenes ; nickel ; radialenes ; radical reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of hexakis(dibromomethyl)benzene with [(Bu3P)2-Ni(COD)] (COD = 1,5-cyclooctadiene) in DMF at 65-70°C yielded a mixture of the title compounds. The mixture was separated by column chromatography to yield hexabromotricyclobutabenzene (3 a) and hexabromohexaradialene (4) in 24 and 16% yields, respectively. 1H and 13C NMR spectroscopy suggest that 3 is obtained as the syn-all-trans isomer 3 a, and the symmetric anti-all-trans isomer 3 b is not obtained at all. The X-ray structures of 3 a and 4 are reported. The hexaradialene 4 has a chair conformation, and deviates from planarity by 43.6°. Heat or radical impurities cause the clean transformation of 3 a to 4.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030207
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  • 4
    Electronic Resource
    Electronic Resource
    Meso- und Rac-Decaisopropylstannocen: Stereoisomerie bedingt durch parallele Anordnung zweier Pentaisopropylcyclopentadienyl-Liganden in Schaufelrad-KonformationProfessor Herbert Schumann zum 60. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 751-755 
    Details
    ISSN: 0044-2313
    Keywords: Decaisopropylstannocene ; crystal structure ; CPMAS 119Sn NMR ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Meso- and Rac-Decaisopropylstannocene: Stereoisomerism Caused by Parallel Arrangement of Two Pentaisopropylcyclopentadienyl Ligands in Paddlewheel ConformationDecaisopropylstannocene 1 is the first Decaisopropylmetallocene, where X-ray diffraction data could be successfully refined and the third example of a group 14 Metallocene with a symmetric sandwich structure. Due to the directionality of the isopropyl substituents 1 occurs as a mixture of diastereomers in the crystalline state as well as in solution. The stereoisomers exhibit the expected signals in solution (1H and 13C NMR) and in the crystal (CPMAS 119Sn NMR).
    Notes: Decaisopropylstannocen 1 ist das erste Decaisopropylmetallocen, dessen Röntgendiffraktometer-Datensatz erfolgreich verfeinert werden konnte und das dritte Beispiel eines Metallocens der Gruppe 14 mit einer symmetrischen Sandwichstruktur. Aufgrund der Direktionalität der Isopropylsubstituenten beider Ringliganden liegt 1 im Kristall und in Lösung als Diastereomerengemisch vor. Die Stereoisomeren zeigen die erwarteten Signale in Lösung (1H- und 13C-NMR) und im Kristall (CPMAS- 119Sn-NMR).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220432
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  • 5
    Electronic Resource
    Electronic Resource
    Reactions of Pentafluorobenzenesulfanylamines (C6F5S)nNH3-n, n = 1, 2, 3 and the Structure of (C6F5S)3NDedicated to Professor Peter Satorius on the Occasion of his 65th Birthday (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 1263-1268 
    Details
    ISSN: 0044-2313
    Keywords: Pentafluorobenzenesulfanylamines ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktionen der Pentafluorobenzolsulfanylamine (C6F5S)nNH3-n, n = 1, 2, 3 und Struktur des (C6F5S)3NAusgehend von (C6F5S)2NX (X = SiMe3 und ½b Hg) hergestellt und charakterisiert werden. In einer Vielzahl von Versuchen, wie z. B. Oxydation bzw. Photolyse ließ sich zeigen, daß die SN-Bindung in (C6F5S)2NH unter Bildung von C6F5SSC6F5 gespalten wird. Es konnte nachgewiesen werden, daß (C6F5S)3N chemisch wenig reaktiv ist; in der Kristallstrukturanalyse besitzen die Moleküle annähernd Cs-Symmetrie. Massen- und 13C-NMR-Spektren für (C6F5S)nNH3-n werden erstmals aufgeführt.
    Notes: The crystal structure of (C6F5S)3N has been examined. The compounds (C6F5S)2NX, X = SiMe3 and ½ Hg have been prepared from (C6F5S)2NH and characterised. In a number of other reactions, such as oxidation and irradiation, the S—N bond in (C6F5S)2NH was readily fractured, forming the disulfide, (C6F5S)2. The compound (C6F5S)3N has been found to be unreactive. Details of the mass and 13C NMR spectra of (C6F5S)nNH3-n, n = 1, 2, 3 are reported.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220726
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