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
Authors:
- 1 November 1992
- journal article
- research article
- Published by Wiley in Journal of Polymer Science Part A: Polymer Chemistry
- Vol. 30 (12) , 2601-2617
Abstract
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 TiMe(1) and TiMe(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.Keywords
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