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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 615-619 
    ISSN: 0009-2940
    Keywords: Self-assembly ; NMR spectroscopy ; Titanium ; Catechol ligands ; Helical structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The racemization/symmetrization of helicate- or meso-helicate-type dinuclear titanium(IV) complexes Mn[(ligand)3Ti2] (n = 4: M = Li, Na, K, Cs; n = 2: M = Ca, Sr), which are formed by metal-directed self-assembly of alkyl-bridged bis(catecholate) ligands in the presence of basic alkali-metal or alkaline-earth metal salts, can be monitored by dynamic NMR spectroscopy. The free-energy barrier (ΔG
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-1948
    Keywords: Azabutadienes ; Tricarbonyliron complexes ; Transfer reagents ; Molecular structure ; Fluxionality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (η4-1-azabuta-1,3-diene)tricarbonyliron complexes 10 are easily prepared in high yield by condensation of the corresponding arylamines 7 with the cinnamaldehydes 8 and subsequent ultrasound-promoted complexation of the resulting 1-azabuta-1,3-dienes 9 with nonacarbonyldiiron. The complexes 10 are shown to represent excellent reagents for the transfer of the tricarbonyliron fragment onto cyclohexa-1,3-diene (1a). The structural characterization for the complexes 10 is achieved by IR, 1H-NMR, and 13C-NMR spectroscopy, as well as X-ray crystallography of 10b, 10c, and 10l. Using variable temperature 13C-NMR spectroscopy the fluxionality of the complexes 10a, 10b, 10c, 10e, and 2 is investigated and the activation barrier for the turnstile rotation of the tricarbonyliron fragment is determined. The transfer reaction and the structural factors influencing the transfer of the tricarbonyliron fragment are extensively investigated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 1264-1268 
    ISSN: 0947-6539
    Keywords: catechols ; cryptates ; helicates ; NMR spectroscopy ; titanium complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of three equivalents of alkyl-bridged biscatechol ligands (1-3)-H4 with two equivalents of [(acac)2TiO] in the presence of two equivalents of alkalimetal carbonate (M = Na, K) affords helicate- or meso-helicate-type supramolecular coordination compounds by spontaneous self-assembly processes. The cryptand-type structure of the binuclear tetraanions [(1)3Ti2]4- or [(2)3Ti2]4- permits inclusion of sodium cations; this was observed by 23Na NMR spectroscopy in solution. Competition experiments with potassium or lithium cations revealed that potassium but not lithium easily displaces the sodium ions from the cavity. Titration experiments indicated that the binding constant for potassium is significantly higher than for sodium. On the other hand, for the large tetraanion [(3)3Ti2]4- with hexamethylene spacers, no binding of alkali-metal ions could be observed by NMR spectroscopy in solution. In the solid state, however, two potassium ions could be incorporated in the interior of the cryptand-type helicate.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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