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Comparative Theoretical Study on Homopolymerization of α-Olefins by Bis(cyclopentadienyl) Zirconocene and Hafnocene: Elemental Propagation and Termination Reactions between Monomers and Metals
journal contribution
posted on 2010-04-12, 00:00 authored by Anniina Laine, Mikko Linnolahti, Tapani A. Pakkanen, John R. Severn, Esa Kokko, Anneli PakkanenA comparative quantum chemical study has been performed to shed light on the fundamental differences between hafnocenes and zirconocenes concerning reactions between the metals and α-olefin monomers, namely, ethene, propene, 1-butene, and 1-hexene. Analogous species along the α-olefin polymerization pathways were studied for bis(cyclopentadienyl) zirconocene and hafnocene, taking into account the structural variations of the first two monomer insertion steps and of the competitive chain-termination reactions. The results were analyzed as a function of both the metal and the monomer, the metal showing more distinct differences. The most notable difference in the reactions of the zirconocene and hafnocene can be seen in β-hydrogen transfer to metal, activation energies for which are significantly higher for the hafnocene.