A New Cocatalyst for Metallocene Complexes in Olefin Polymerization

Activation of metallocene complexes for olefin polymerization reactions can only be achieved by a relatively short list of special cocatalysts: dialkylaluminum chlorides, which work well only with titanocenes, trialkylaluminum compounds being very poor cocatalysts for metallocene complexes); alkylalumoxanes; a combination of trimethylaluminum and dimethyl- aluminum fluoride; compounds or salts generating noncoordinative anions such as [R sub 3 NH] exp + [B(C sub 6 F sub 5 ) sub 4 ] exp - , We have discovered a new type of cocatalyst which is capable of activating metallocene complexes in olefin polymerization reactions. This cocatalyst has two components: a haloorganoaluminum compound Al sub n R sub m X sub 3n-m (for example, AlEt sub 2 Cl and a dialkylmagnesium compound MgR' sub 2 (R' = 1 butyl, hexyl etc.). These compounds are used at a molar [Al]:[Mg] ratio of greater than 2. In the case of zirconocene complexes, each of the components, if used alone, does not produce an olefin polymerization catalyst. However, when these components are mixed, they readily activate metallocene complexes for polymerization reactions.