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  • 1
    Electronic Resource
    Electronic Resource
    Alcoholysis of Aluminum Alkyls Supported by Bulky Phenoxide Ligands: Synthesis, Characterization, and ε-Caprolactone Polymerization Activity of Two Dimeric Aluminum Isopropoxides (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 441-445 
    Details
    ISSN: 1434-1948
    Keywords: Aluminum ; Alkoxides ; Lactone ; Ring-opening ; Polymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of trialkylaluminum Al2R6 (R = Me, Et) with 2,2′-methylenebis(6-tert-butyl-4-methylphenol) (mbmpH2) gives the dimeric mono(alkyl) complex [Al(mbmp)R]2 with bridging oxygen atoms. Reaction of [Al(mbmp)R]2 with one equiv. of 2-propanol results in the formation of the dimeric isopropoxide [Al(mbmp)(μ-OiPr)]2. Single-crystal X-ray analysis shows a C2h-symmetric structure with a planar Al2O2 core. Monomeric methylbis(2,6-di-tert-butyl-4-methylphenolato)aluminum, AlMe(OC6H2-2,6-tBu2-4-Me)2 (MAD), was found to react with one equiv. of 2-propanol to give a dimeric isopropoxide [AlMe(OC6H2-2,6-tBu2-4-Me)(μ-OiPr)]2 in which the bulky phenolate, instead of the methyl group, has been displaced. According to the single-crystal X-ray structure analysis, the molecule contains a similar Al2O2 core, but the two 2,6-di-tert-butyl-4-methylphenolato ligands are cis- and orthogonally arranged to each other. ε-Caprolactone is polymerized at 50 °C in toluene in a controlled manner by [Al(mbmp)(μ-OiPr)]2, to give poly(ε-caprolactone) with high molecular weights and narrow molecular weight distributions (Mw/Mn 〈 1.50). The low efficiency values (number of polymer chains initiated per aluminum atom) imply that [Al(mbmp)(μ-OiPr)]2 exists in a monomer-dimer equilibrium. The polymerization of ε-caprolactone by [AlMe(OC6H2-2,6-tBu2-4-Me)(μ-OiPr)]2 is faster, but somewhat less controlled.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Silanolato-Komplexe von Titan und Zirconium. Die Kristallstrukturen von Cp2TiCl(OSiPh3) und Cp2ZrCl(OSiPh3) (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1719-1724 
    Details
    ISSN: 0044-2313
    Keywords: Silanolato Complexes of Titanium and Zirconium ; Synthesis ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Silanolato Complexes of Titanium and Zirconium. The Crystal Structures of Cp2TiCl(OSiPh3) and Cp2ZrCl(OSiPh3)The title compounds have been prepared by the reaction of Cp2MCl2 (M = Ti, Zr) with triphenylsilanole in diethylether in the presence of piperidine. They form only sparingly moisture sensitive orange (Ti) or colourless (Zr) crystal needles, which were characterized by X-ray crystallography.Cp2TiCl(OSiPh3): Space group P21/n, Z = 4, structure solution with 3961 observed unique reflections, R = 0.057. Lattice dimensions at 20°C: a = 1029.6, b = 1719.3, c = 1388.9 pm, β = 100.69°. The compound forms monomeric molecules with bond lengths TiO of 184.2 pm, SiO of 161.5 pm, and a TiOSi bonding angle of 164.5°.Cp2ZrCl(OSiPh3): Space group P3, Z = 18, structure solution with 2799 observed unique reflections, R = 0.047. Lattice dimensions at -20°C: a = b = 3518, c = 1058.3 pm. The structure consists of three symmetry-independent monomeric molecules, which differ only slightly. The bond lengths are (in average): ZrO 196.4 pm, SiO 162.1 pm, the ZrOSi bond angle is 173.7°.
    Notes: Die Titelverbindungen werden aus Cp2MCl2 (M = Ti, Zr) und Triphenylsilanol in Diethylether in Gegenwart von Piperidin hergestellt. Sie bilden nur wenig feuchtigkeits-empfindliche orange (Ti) bzw. farblose Kristallnadeln (Zr), die wir kristallographisch charakterisiert haben.Cp2TiCl(OSiPh3): Raumgruppe P21/n, Z = 4, Strukturlösung mit 3961 unabhängigen, beobachteten Reflexen, R = 0,057. Gitterkonstanten bei -50°C: a = 1029,6; b = 1719,3; c = 1388,9 pm, β = 100,69°. Die Verbindung bildet monomere Moleküle mit Abständen TiO von 184,2 pm, SiO von 161,5 pm und einem TiOSi-Bindungswinkel von 164,5°.Cp2ZrCl(OSiPh3): Raumgruppe P3, Z = 18, Strukturlösung mit 2799 unabhängigen, beobachteten Reflexen, R = 0,047. Gitterkonstanten bei -20°C: a = b = 3518; c = 1058,3 pm. Die Struktur enthält drei symmetrieunabhängige monomere Moleküle, die sich nur wenig voneinander unterscheiden. Die Abstände ZrO betragen im Mittel 196,4 pm, SiO im Mittel 162,1 pm und die Bindungswinkel ZrOSi im Mittel 173,7°.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946201010
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