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  • 1
    Electronic Resource
    Electronic Resource
    Solvay type VCl3 isospecific catalysts (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1807-1817 
    Details
    ISSN: 0887-624X
    Keywords: VCl3 ; propylene polymerization ; Ziegler-Natta catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvay type S-VCl3 catalyst has 7% of catalytically active vanadium sites ([C*]) with kp (rate constant of propagation) = 31 (M s)-1 for ethylene polymerization. Addition of a comonomer, propylene of 4-methylpentene-1 (4-MP) significantly raised the ethylene polymerization activity. S-VCI3 catalyst has very small amounts of catalytically active vanadium for propylene polymerizations: [Ci*] = 0.19% with kp,i = 857 (M s)-1 and [Ca*] = 0.45% with kp,a = 23 (M s)-1 for isospecific and nonspecific sites, respectively. Addition of a conomer, ethylene or 4-MP. lowered the propylene polymerization activity. S-VCI3 is more easily reduced to the divalent ion by AIR3 than S-TiCl3. Methyl-p-toluate moderates the reducting power of AIR3; it increase the productivity and stereoselectivity of the S-YiCl3 catalyst, VCI3 supported on MgCl2 (CW-V catalyst) has enhanced rate constant of propylene polymerization but has the opposite effects on the S-TiCl3 Catalyst. VCI3 supported on MgCl2 (CW-V catalyst) has enhances rate constant of propylene polymerization but only a minute fraction of the supported vanadiums are catalytically active: [Ci*] = 0.019% and kp,i = 1580 (Ms)-1, [Ca*] = 0.057% and kp,i = 58 (M s)-1. This is compared with far greater number of catalytically active titanium sites in the TiCl3 supported on MgCl2 catalyst: [Ci*] = 6% and kp,i = 200 (M s)-1, [Ca*] = 6% and kp,a = 16(M s)-1. Therefore, both the S-VCI3 and CW-V catalysts are highly stereoselective but low in efficiency with respect to the utilization of the vanadium ion in the catalysis.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080291213
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  • 2
    Electronic Resource
    Electronic Resource
    Silolene-Bridged zirconocenium polymerization catalysts (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 149-158 
    Details
    ISSN: 0887-624X
    Keywords: metallocene ; stereoselective catalyst ; propylene polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new silolene-bridged compound, racemic (1,4-butanediyl) silylene-bis (1-η5-in-denyl) dichlorozirconium (1) was synthesized by reacting ZrCl4 with C4H8Si (IndLi)2 in THF. 1 was reacted with trialkylaluminum and then with triphenylcarbenium tetrakis (penta-fluorophenyl) borate (2) to produce in situ the zirconocenium ion (1+). This “constraint geometry” catalyst is exceedingly stereoselective for propylene polymerization at low temperature (Tp = -55°C), producing refluxing n-heptane insoluble isotactic poly(propylene) (i-PP) with a yield of 99.4%, Tm = 164.3°C, δHf = 20.22 cal/g and M̄w = 350 000. It has catalytic activities of 107-108 g PP/(mol Zr · [C3H6] · h) in propylene polymerization at the Tp ranging from -55°C to 70°C, and 108 polymer/(mol Zr · [monomer] · h) in ethylene polymerization. The stereospecificity of 1+ decreases gradually as Tp approaches 20°C. At higher temperatures the catalytic species rapidly loses stereochemical control. Under all experimental conditions 1+ is more stereospecific than the analogous cation derived from rac-dimethylsilylenebis (1-η5-indenyl)dichlorozirconium (4). The variations of polymerization activities in ethylene and in propylene for Tp from -55°C to +70°C indicates a Michaelis Mention kinetics. The zirconocenium-propylene π-complex has a larger insertion rate constant but lower thermal stability than the corresponding ethylene π-complex. This catalyst copolymerizes ethylene and propylene with reactivity ratios of comparable magnitude rE ˜ 4rp. Furthermore, rE.rp ˜ 0.5 indicating random copolymer formation. Both 1 and 4 activated with methylaluminoxane (MAO) exhibit much slower polymerization rates, and, under certain conditions, a lower stereo-selectivity than the corresponding 1+ or 4+ system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320117
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Heptane-soluble homogeneous zirconocene catalyst: Synthesis of a single diastereomer, polymerization catalysis, and effect of silica supports (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2093-2108 
    Details
    ISSN: 0887-624X
    Keywords: zirconocene ; ethylene polymerization ; propylene polymerization ; silica-supported catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(1-indenyl)-di[1′S, 2′R, 5′S)-methoxy]silane (1) was converted into a mixture of corresponding ansa-diastereomeric zirconocenes. Further purification afforded a single dia-stereomer, di[(1′S, 2′R, 5′S)-methoxy] silylene-bis[η5-1(R, R)-(+)-indenyl] dichlorozirconium (2), which is optically active and hydrocarbon soluble. Extremely rapid ethylene, propylene, and ethylene-hexene polymerizations were observed both in toluene and n-heptane solutions; for instance, at 50°C, activity for ethylene polymerization reaches ∼ 1.5×1010 (g of PE/((mol of Zr) · [C2H4] · h). The “bare” zirconocenium ion generated from 2/TIBA/Ph3CB(C6F5)4 exhibits unusual polymerization behaviors; the polymerization activity increases monotonically with temperature of polymerization (Tp) up to a conventional polymerization condition (50-70°C), and the 13C NMR study shows that the isotactic poly-propylene obtained has fairly high [mmmm] methyl pentad distributions at high Tp (≤25°C with [mmmm] ∼ 0.93-0.75) and a perfect stereoregularity at low Tp (≤0°C with [mmmm] 〉 0.99). The catalyst precursors 2 and Et(Ind)2ZrCl2 (3) supported on silica by different approaches produced poly(olefins) of different molecular weights and stereoregularities, and a methylaluminokane and Ph3CB(C6F5)4 free silica-supported zirconocene system was found to be activated by triisobutylaluminum. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331301
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    Paper (German National Licenses)
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