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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Organometallics 12 (1993), S. 2660-2667 
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 5393-5405 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new two-dimensional 2H magic-angle-spinning NMR experiment to study paramagnetic compounds is presented. It can be carried out by the two-pulse sequence (90°)–(t1)–(180°)–(t2, acquisition) or the three-pulse sequence (90°)–(t1)–(54.7°)–(τ)–(125.3°)–(t2, acquisition). The latter has the advantages over the former in that pure-absorption spectra can be obtained, and also finite pulse-width effects are less apparent. The intensities of the two-dimensionally spread sidebands are calculated as a function of the paramagnetic and the quadrupole coupling parameters, the time-evolution of the spin system during the rf pulse being involved. The method is applied to paramagnetic coordination compounds with selectively deuterated acetate groups: Mn2O(O2CCD3)2{(C3H3N2)2BH}2 and Pr(O2CCD3)3⋅H2O. The principal values of the two interaction tensors can be separately estimated from the projections of the two-dimensional spectrum onto the corresponding diagonals. These values are further refined by simulations of the two-dimensional spinning sideband pattern, which also allows us to determine the mutual orientation of the two tensors. The paramagnetic shift tensors are calculated on the basis of the crystal structures and are compared with those obtained by the experiments. The effect of the bulk magnetic susceptibility on the observed paramagnetic shift tensor is discussed. Some methods to remove this effect are suggested. © 1997 American Institute of Physics.
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 237-244 
    ISSN: 1434-1948
    Keywords: Titanium complexes ; Amido-cyclopentadienyl ligand ; Titanium alkyl ; Intramolecular coordination ; Ethene polymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titanium complexes containing a linked isopropyl- or benzylamido(tetramethylcyclopentadienyl) ligand C5Me4SiMe2NR (R = iPr, CH2Ph,) and one bidentate organyl group C6H4(CH2NMe2)-2, CH2C6H4(NMe2)-2, and {η5-C5H3(CH2NMe2)-2}Fe(η5-C5H5) were prepared by salt metathesis of the corresponding dichloro complex Ti(η5:η1-C5Me4SiMe2NR)Cl2 with the lithium organyl. Single crystal X-ray structural analysis of Ti(η5:η1-C5Me4SiMe2NCH2Ph)- {C6H4(CH2NMe2)-2}Cl and of Ti(η5:η1-C5Me4SiMe2NiPr){CH2C6H4(NMe2)-2}Cl revealed the presence of intramolecular coordination with square pyramidal geometry around titanium. In the ferrocenyl derivative Ti(η5:η1-C5Me4SiMe2NCH2Ph)[{η5-C5H3(CH2NMe2)-2}Fe(η5-C5H5)]Cl the NMe2 group is not bonded at the titanium atom. Ethene polymerization catalyzed by these complexes upon activation with methylaluminoxane was examined.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1263-1268 
    ISSN: 1434-1948
    Keywords: Cluster chemistry ; Silaborane clusters ; Carbonyl complexes ; Silicon coordination ; Ruthenium complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction between three equivalents of the silaborate [NEt4][MeSiB10H12] (2) and one equivalent of [Ru3(CO)12] resulted in almost quantitative formation of the mononuclear transition metal complex [NEt4][Ru(CO)3(η5-MeSiB10H10)] (5), which was characterized by X-ray structure analysis. The trinuclear ruthenium complex [NEt4][Ru3(CO)8(η5-MeSiB10H10)] (7) was synthesized in high yield from the reaction of one equivalent of 2 and [Ru3(CO)12]. The cluster 7 reacts with two equivalents of PMe2Ph with substitution of two carbonyl groups to give the substitution product [NEt4][Ru3(CO)6(PMe2Ph)2(η5-MeSiB10H10)] (8).
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  • 7
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1429-1431 
    ISSN: 0009-2940
    Keywords: Titanium complexes ; Amido-cyclopentadienyl ligand ; Optically active complexes ; Asymmetric hydrogenation catalysts ; Conformational rigidity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically active titanium complexes of the formula Ti(η5:η1-C5R4SiMe2NCHMePh)Cl2 (R = H, Me), containing the cyclopentadienyl ligand linked to a chiral 1-phenylethylamido moiety, were synthesized and characterized in both enantiomerically pure forms. A single-crystal X-ray structural analysis of (S)—(—)Ti(η5:η1-C5H4SiMe2NCHMePh)Cl2 shows a conformation in which the phenyl group is turned away from the metal center. NOE measurements suggest that a related structure is retained in solution. Upon activation with n-butyllithium, these complexes show hydrogenation activity toward imines with slight enantioselectivity.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 209-215 
    ISSN: 0009-2940
    Keywords: Titanium ; Amidocyclopentadienyl ligand ; Alkyltitanium compounds ; Lewis acids ; Agostic interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titanium complexes of the general type Ti(η5:η1-C5H4Si-Me2NCH2C6H3X2-2,5)Cl2 (X=H, F), containing a linked benzylamido-cyclopentadienyl ligand, were prepared by reaction of Ti(η5-C5H4SiMe2Cl)Cl3 with lithium amide Li(NHCH2C6H3X2-2,5). A single-crystal X-ray structural analysis of Ti(η5: η1-C5H4SiME2NCH2C6H3F2-2,5)Cl2 revealed a conformation in the solid state in which the aryl ring is turned away from the metal center. Ti(η5:η1-C5H4SiMe2NCH2C6H5)Cl2 can be alkylated with a variety of reagents to form extremely sensitive complexes of the type Ti(η5-C5H4SiMe,2NCH2C6H5)R2 (R=Me, CH2 C6H5, CH2SiME3, CH2CMe2C6H5). Reaction of Li2[C5Me4SiMe2NCH2C6H5] with TiCl3(THF)3 gave Ti(η5: η1-C5Me4SiMe2NCH2C6H5)Cl2, which can also be alkylated to form dialkyl complexes of the type Ti(η5:η1-C5Me4SiMe2NCH2C6H5)R2(R=Me, CH2C6H5, CH2SiMe3, C6H5).A single-crystal X-ray structural analysis of Ti(η5:η1-C5Me4SiMe2NCH2C6H5)(CH2C6H5)2 suggests the presence of α-agostic bonding of one of the titanium-bound CH2C6H5 groups to the titanium center.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 91-92 
    ISSN: 0009-2940
    Keywords: Boranes, amino(imino) ; Iron, tricarbonyl(butanone) ; Diiron, [(boryloxy)allyl]hexacarbonyl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Formation of a Fe2(CO)6 Complex with a (Boryloxy)allyl BridgeThe amino(imino)borane Me3Si(tBu)N=B=NtBu (1) reacts with (benzylideneacetone)tricarbonyliron (2) in 1:2 molar ratio to give a 50% yield of the hexacarbonyldiiron complex 3 with a fly-over (boryloxy)allyl bridge, which crystallizes in the space group P21/c. The structure of 3 can be described as a pyramid with Fe(CO)3 at the apex and a non-planar pentagon [-Fe(CO)3-O(BXX′)-C(Me)-CH-C(Ph)-] [X = NHtBu, X′ = N(SiMe3)tBu] as the basis, but there is no bond between the apex and the O atom.
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