Nature of the Active Sites in Soluble Ziegler-Polymerization Catalysts Generated from Titanocene Halides and Organoaluminum Lewis Acids
That the active site in Ziegler-Natta polymerization catalysts is the transition metal-carbon bond receives strong support from the finding that pure transition metal alkyls, such as tetrabenzyltitanium , can themselves polymerize ethylene and propylene, even in the complete absence of any main-group alkyl. However, it is also evident that combinations of transition-metal salts or organometallics with main-group alkyls often display greatly enhanced catalytic activity and stereoregular polymerization in such processes . The isotactic polymerization of propylene by TiCl3 and Et2AlCl  and the greatly accelerated polymerization of ethylene by Cp2ZrMe2 and (MeAlO)n  are cases in point.
KeywordsEthylene Polymerization Polymerization Catalyst Titanocene Dichloride Insertion Product Allylation Product
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