Counterion effect on coordination and insertion steps of Olefin Polymerization Catalysts

BELELLI, PATRICIA GABRIELA; CASTELLANI, NORBERTO JORGE

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

Elsevier

Año: 2006 vol. 253 p. 52 - 61

1381-1169

A theoretical analysis of coordination and insertion of the ethylene molecule on different metallocenic active sites was performed. The sites were modeled as ionic-pairs where the counterion is close to the cation. The steps going from the isolated species ionic-pairs and the monomer to the new propyl group linked to the ionic-pair were calculated and analyzed. The influence of the counterion on the energy barrier that the olefin must overcome for its coordination and insertion into the Zr-CCH3 bond was considered. The energy barrier is decreased by the inclusion of an AlCl3 additive. As an additional study, the presence of a second ethylene molecule in the neighborhood of the active site was evaluated. This situation reduces the maximum energy and improves the stability of the final propyl ionic-pair.