Metallocene catalysts for olefin polymerizations. XXIV. Stereoblock propylene polymerization catalyzed by rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl)(1-η5-indenyl)dimethyltitanium: A two-state propagation

Racemic‐anti‐[ethylidene(1‐η5‐tetramethylcyclopentadienyl) (1‐η5‐indenyl)dimethyltitanium (6) has been synthesized and its molecular structure determined by x‐ray diffraction methods. The two TiMe(1) and TiMe(2) units have bond distances differing by 0.08 Å and their proton NMR resonances are sepa...

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Published in:Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 1992-11, Vol.30 (12), p.2601-2617
Main Authors: Chien, James C. W., Llinas, Geraldo Hidalgo, Rausch, Marvin D., Lin, Ye-Gang, Winter, H. Henning, Atwood, Jerry L., Bott, Simon G.
Format: Article
Language:English
Subjects:
ansa-metallocene catalyst
thermoplastic elastomeric poly(propylene)
Ziegler-Natta catalysts
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Summary:Racemic‐anti‐[ethylidene(1‐η5‐tetramethylcyclopentadienyl) (1‐η5‐indenyl)dimethyltitanium (6) has been synthesized and its molecular structure determined by x‐ray diffraction methods. The two TiMe(1) and TiMe(2) units have bond distances differing by 0.08 Å and their proton NMR resonances are separated by over 1 ppm. Using this compound and methylaluminoxane (MAO) as the activator, at 25°C the 6/MAO catalyst produced polypropylene having crystalline domain with physical crosslinks. The polymers obtained at lower polymerization temperatures are rheologically liquids. The behaviors of this catalyst system resembles closely the previously reported rac‐[anti‐ethylidene(1‐η5‐tetramethylcyclopentadienyl) (1‐η5‐indenyl)dichlorotitanium (4)/MAO system. The structure of 6 determined here furnishes tangible support for the proposed two‐state (isomeric)‐switching propagation mechanism. Addition of MAO to 6 causes broadening of the Me(1) resonance in the 1H‐NMR spectra, and 6 is decomposed by Ph3C+B(C6F5)‐4. © 1992 John Wiley & Sons, Inc.
ISSN:0887-624X
1099-0518
DOI:10.1002/pola.1992.080301215