Ru-based olefin metathesis catalysts bearing ph-responsive n-heterocyclic carbene (NHC) ligands: Activity control via degree of protonation

Shawna L. Balof, Bing Yu, Andrew B. Lowe, Yan Ling, Yong Zhang, Hans Jörg Schanz

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

Olefin metathesis catalysts (H2ITap)(PCy3)Cl2Ru=CHPh (4)and (H2ITap)Cl2Ru=CH-(C6H4-O-iPr) (5)[H2ITap = 1,3-bis-(2-,6-dimethyl-4- dimethylaminophenyl)-4,5-dihydroimid-azol-2-ylidene] were used for the ring-opening metathesispolymerization (ROMP) of exo-7-oxanorbornene derivative 7in the presence of various amounts of acid. Upon gradualprotonation of the NMe2 groups of the H2Tap ligand, the me-tathesis activity of both catalysts were gradually reduced dueto electronic changes of the N-heterocyclic carbene (NHC)ligand donor capability. The investigation of the ROMP poly-mer 8, DFT calculations and measurements of the initiationkinetics prove that the reduced activity is solely due to re-duced rates of propagation.

Original languageEnglish
Pages (from-to)1717-1722
Number of pages6
JournalEuropean Journal of Inorganic Chemistry
Issue number13 SPEC. ISS.
DOIs
StatePublished - May 2009

Keywords

  • Carbene ligands
  • Densityfunctional calculations
  • Metathesis
  • N-Heterocyclic carbenes
  • Ring-opening polymerization
  • Ruthenium

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