Moving up and down the titanium oxidation state in Ziegler-Natta catalysis

Naeimeh Bahri-Laleh*, Andrea Correa, Shahram Mehdipour-Ataei, Hassan Arabi, Mehdi Nekoomanesh Haghighi, Gholamhosein Zohuri, Luigi Cavallo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

DFT molecular modeling studies were undertaken to shed light on possible activation and deactivation mechanisms of Ziegler-Natta catalytic systems, as well as on the possible mechanisms for their reactivation by organohalides. We focused our efforts on Ti species attached to the (110) lateral cut of MgCl 2. First, the possible activation of adsorbed TiCl4 leading to an adsorbed TiIII species bearing a Ti-alkyl bond and a coordination vacancy, which is a species able to undergo chain-growth, was considered. According to our calculations formation of the first active species can be easily rationalized by cleavage of a Ti-Cl bond of coordinated TiCl 4 by AlEt3, followed by transalkylation promoted by another AlEt3 molecule. Second, we investigated the possible reduction of polymerization active TiIII species leading to polymerization inactive TiII species, and we found that a Ti-H bond, possibly formed after chain termination, is weaker than the Ti-Et (polymeryl) bond. Third, we investigated the mechanism of reactivation of TiII species by organohalides, and it was concluded that reoxidation by Cl rich organohalides is thermodynamically more favored.

Original languageEnglish (US)
Pages (from-to)778-783
Number of pages6
JournalMacromolecules
Volume44
Issue number4
DOIs
StatePublished - Feb 22 2011

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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