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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2059-2061 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impact of electron heating on vertical electrical transport in superlattices is shown to cause an S-shaped current–voltage characteristic in addition to the conventional N type occurring at lower fields. Our calculations are supported by experimental data. The combination of S- and N-type instabilities leads to a modified structure of the high-field domains associated with self-generated GHz oscillations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 789-793 
    ISSN: 1434-1948
    Keywords: Boranes ; Carbenes ; Heterocycles ; Imidazoles ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nucleophilic carbene 3-borane-1,4,5-trimethylimidazol-2-ylidene anion (1-) reacts with the electrophiles CH3I, (CH3)3SiCl, (CH3)3SnCl, and the bromodiazaboroline 7 to form the 2-substituted imidazoles 4, 5, 6, and 8. With triethylborane, the anionic carbene borane adduct 9- is obtained. An unexpected result was achieved when chlorodimethoxyborane and HBCl2 · S(CH3)2 were used as electrophiles. In both cases only the imidazabole 14a could be isolated. Imidazole 5, the imidazole borane adduct 3a and the imidazabole 14a were characterized by X-ray structure analyses.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 843-849 
    ISSN: 1434-1948
    Keywords: Boranes ; Carbenes ; Carbene complexes ; Heterocycles ; Imidazoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of the Lewis acids BH3 and BEt3 with trimethylimidazole (1) lead to the borane adducts 2a and 2b. Deprotonation of 2a with n-butyllithium results in the formation of the novel N-borane-substituted imidazol-2-ylidene anion 3a- whereas deprotonated 2b rearranges unexpectedly to the anionic compound 3b-. This can be transformed into the carbene-borane adduct 4 by methylation. The reaction of 3a- with [Mn(CO)5Br] yields the carbene complex 5. Surprisingly, 3a- attacks Fe(CO)5 at a carbon atom which leads to the iron acyl complex anion 6-. The compositions of the products follow from spectroscopic and analytical data and from X-ray structure analyses for Li(thp)+3a-, Li(thf)2+3b- and Li(thp)3+6-.
    Type of Medium: Electronic Resource
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