Evolution of the Titanium-Aluminum System

The eflRciency or activity of these early catalyst systems was, however, low. The term activity, as it is used in most literature references, refers to the rate of polymerization, and is often expressed in terms of kilograms of polymer formed per gram of catalyst. Because of low activity, substantial amounts of catalyst were needed to achieve acceptable yields of polymer, and 

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Most titanium(IV) alkyls tend to be reduced by aluminum alkyls in a complicated sequence of reactions accompanied by evolution of alkane and alkene. The catalytic activity of the bis(cyclopentadienyl)titanium-aluminum complexes is associated with the titanium alkyl. Hence, it is very interesting to investigate the mechanism of any reductive reaction. In order to study side reactions in the absence of polymerization, highly alkylated systems completely free of halogen are preferred. Moreover, reduction takes place much faster, the higher the alkyl-group content of the added aluminum alkyl. 

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