Relationship between regiospecificity and type of stereospecificity in propene polymerization with zirconocene-based catalysts

Gaetano Guerra*, Pasquale Longo, Luigi Cavallo, Paolo Corradini, Luigi Resconi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

104 Scopus citations

Abstract

The microstructures of polypropenes produced with several zirconocene- based catalyst systems are compared, to verify the possible correlation between the type of stereospecificity and the amount of regioirregularities. It is confirmed that, while syndiospecific and aspecific zirconocenes are highly regiospecific, isospecific systems produce substantial amounts of regioirregular monomeric units. The amount of these secondary units strongly depends on the nature of the π-ligands and on the type of the bridge connecting them. Molecular mechanics calculations are reported, indicating that the intermediates which are energetically suitable for the secondary and primary insertions, for isospecific or syndiospecific complexes, coordinate monomer enantiofaces of the opposite or the same chirality, respectively. This difference accounts for the lower regiospecificity of the isospecific catalytic complexes, assuming that the energy barrier for the rotation of the coordinated monomer around the metal-olefin bond, between the orientations suitable for the primary and secondary insertions is lower than (or comparable to) the activation energy for secondary monomer insertion.

Original languageEnglish (US)
Pages (from-to)4394-4403
Number of pages10
JournalJournal of the American Chemical Society
Volume119
Issue number19
DOIs
StatePublished - May 14 1997

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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