Polymeric systems displacement moves

In the regular and real olefin polymerization processes with metallocene catalysts, the anion is an ever-present participant and an integral part of the functioning catalyst system. It is systematically displaced and moves (in and) out of the coordination sphere in a concerted action, while the monomer units approach for coordination to be paired again with the cation after the insertion process is complete. Assuming that the monomer approach proceeds along the most favorable path (i.e., via a cis approach with respect to the anion), immediately after the monomer insertion the anion is positioned at the outer coordination sphere, on the side of the polymer chain (Fig. 20a). 

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