Influence of the ligand structure of hafnocene polymerization catalysts: A theoretical study on chain termination reactions in ethene polymerization

Ligand effects on chain termination reactions in hafnocene-catalyzed ethene polymerization process have been systematically studied by quantum chemical methods. β-hydrogen transfer to metal, β-hydrogen transfer to monomer and hydrogenolysis were studied for 27 hafnocenes, initiating the chain termination reactions after insertion of the second ethene monomer. The results of the calculations were studied as a function of the ligand structure, focusing on the effects of various ancillary ligands, ligand substituents and bridging units. The ligand effects on chain termination reactions are strongly affected by combined effects of various structural units, in particular, in the cases of β-hydrogen transfer to monomer and hydrogenolysis. The results are expected to aid in design and development of new hafnocene polymerization catalysts.

The influence of ligand structure of hafnocene catalysts on chain termination has been studied by quantum chemical methods. Three mechanisms were considered: β-hydrogen transfer to metal, β-hydrogen transfer to monomer, and hydrogenolysis. Altogether 27 hafnocenes with different bridges, ligands and ligand substituents were included in the analysis.Figure optionsDownload as PowerPoint slide