Ethylene Polymerization by Zirconocene Catalysis

The production of polyethylene by zirconocene catalysis is a multistep process that includes initiation, propagation, and termination. Each of these steps has a number of associated equilibrium and transition state structures. These structures have been studied in the gas-phase environment using density functional and integrated methods. We have also examined the effects of solvation upon the energetics of the various polymerization steps employing continuum and explicit representations of the solvent (toluene). The reaction steps we have studied are initiation, propagation, propylene and hexene incorporation, termination by hydrogenolysis, termination by β-H transfer to the metal, termination by β-H transfer to the monomer, and reactivation. The solvation effect of toluene takes on special significance for the initiation, termination by hydrogenolysis and by β-H transfer to the metal, and reactivation steps.