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  • 1
    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.
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  • 2
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Oxidative addition to a metal in a low valent state produces catalysts that allow reporter or functional groups to be introduced to a polymer chain end. Substituted allyltrifluoroacetates were added to Ni(0)(COD)2. The resulting π-allyl-Ni trifluoroacetates are dimeric in the solid state as well as in solution. The crystal structure of bis[(η3-2-phenylallyl)(trifluoroacetato)-nickel(II)], bis[(η3-2-trimethylsilylallyl)(trifluoroacetato)nickel(II)], are given and correlated with the reactivity as polymerization catalysts. Butadiene, styrene, and norbornene are used as monomers. The substituent of the allyl group is found quantitatively to be the end group of each macromolecule. Thus it is demonstrated that no chain transfer occurs.
    Additional Material: 8 Ill.
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  • 3
    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.
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  • 4
    ISSN: 0009-2940
    Keywords: Titanium complexes ; Amido-cyclopentadienyl ligand ; Tridentate ligand ; Lewis acidity ; Chelate effect ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new titanium complexes of the general type Ti(η5:η1-C5H4SiMe2NCH2CH2X)Cl2 (X = NMe2 OMe), containing a tridentate ligand, were prepared by reaction of Ti(η5-C5H4Si—Me2Cl)Cl3 with the lithium amide Li(NHCH2CH2X) (X = NMe2, OMe). The 1H—NMR chemical shifts for the protons of the ethylene link were found to vary considerably as a function of the temperature, indicating the presence of an equilibrium between the tri- and bidentate bonding mode of the ligand. A single-crystal X-ray structural analysis of Ti(η5:η1—C5H4SiMe2NCH2CH2OMe)Cl2 revealed that the methoxy function is not intramolecularly coordinated in the solid state.
    Additional Material: 1 Ill.
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  • 5
    ISSN: 0009-2940
    Keywords: Titanium complexes ; Bidentate phenoxy ligands ; Bulky phenols ; Lewis acidity ; Pentacoordination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new titanium complexes of the general type Ti(mbmp)X2 (X = Br, I; OMe, OiPr, OtBu), containing a bidentate bis(phenoxy) ligand derived from 2,2′-methylenebis(6-tert-butyl-4-methylphenol) (mbmpH2), was prepared. The 1H-chemical shifts for the protons of the methylene link were found to vary considerably as a function of the ligand X. Reaction of Ti(OiPr)4 with two equivalents of mbmpH2 gave the C2-symmetric spiro-titanate complex Ti(mbmp)2. The crystalline labile solvent adducts of the dichloro complex Ti(mbmp)Cl2 with THF and DME were isolated and characterized. A single-crystal X-ray structural analysis revealed the THF adduct to be a mono(THF) adduct with a trigonal-bipyramidal configuration, the bidentate mbmp ligand spanning an apical and equatorial site and the THF ligand occupying the remaining apical position.
    Additional Material: 2 Ill.
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  • 6
    ISSN: 0009-2940
    Keywords: Phosphane iminato complexes ; Arsenic compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phosphane Iminato Complexes of Arsenic. Crystal Structures of [AsCl(NPMe3)]2Cl2, [AsCl(NPMe3)2SbCl4]SbCl6, and [AsCl(NPMe3)2SnCl4] · CH3CN[AsCl(NPMe3)]2Cl2 (1) was prepared by the reaction of arsenic trichloride with the silylated phosphane imine Me3-SiNPMe3 in acetonitrile solution. According to the crystal structure determination, 1 has an ionic structure with [AsCl(NPMe3)]22+ ions, in which the As atoms are linked by the μ2-N atoms of the NPMe3- groups. Compound 1 reacts with antimony pentachloride to give [AsCl(NP-Me3)2SbCl4]+SbCl6- (2), with tin tetrachloride to form [AsCl(NPMe3)2SnCl4] (3), which is isoelectronic to the cation of 2. In 2 and 3 AsCl(NPMe3)2 acts as a chelating agent forming and , respectively, four-membered ring structures.
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