Quinoline Pyridine(Imine) Iron Complexes as Catalysts for the 1,4-Hydrovinylation of 1,3-Dienes

Coralie Duchemin, Amelia I. Liu, Junho Kim, Paul J. Chirik

Research output: Contribution to journalArticlepeer-review

Abstract

The synthesis, characterization, and stoichiometric reactivity of a series of quinoline pyridine(imine) (R(R’)Q(R”)PI) (R = 2,6-Me, 2,6-iPr or 2,4,6-Cy; R’ = H or Cl, R″ = H or tBu) iron dichloride complexes is described. Treatment of (QPI)FeCl2 with two equivalents of methyl lithium furnished two examples of the corresponding (QPI)FeCH3 complexes. The molecular structures were established by X-ray diffraction, and the electronic structures were studied by magnetometry, 57Fe Mössbauer spectroscopy, and DFT calculations. The combined data support overall S = 3/2 ground states that are best described as high spin iron(II) complexes engaged in antiferromagnetic coupling with a chelate radical anion, similar to related pyridine(diimine) and terpyridine iron alkyl complexes. Bimolecular reductive elimination of ethane in the presence of butadiene afforded an iron crotyl complex bearing a cyclometalated QPI ligand, formed upon ligand-to-ligand hydrogen transfer (LLHT) or stepwise oxidative addition/reduction elimination from a putative (QPI) iron butadiene intermediate. The cyclometalated QPI iron crotyl complex proved to be a competent catalyst for the hydrovinylation of butadiene with ethylene and produced high selectivity for the hexa-1,4-diene isomer. Deuterium labeling experiments established H/D scrambling between ethylene, butadiene and the QPI ligand, consistent with background transfer hydrogenation reactivity and catalyst decomposition observed during catalysis.

Original languageEnglish (US)
Pages (from-to)3109-3119
Number of pages11
JournalOrganometallics
Volume42
Issue number21
DOIs
StatePublished - Nov 13 2023

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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