Pyridine(diimine) Iron Diene Complexes Relevant to Catalytic [2+2]-Cycloaddition Reactions

C. Rose Kennedy, Hongyu Zhong, Matthew V. Joannou, Paul J. Chirik

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The synthesis, characterization, and catalytic activity of pyridine(diimine) iron piperylene and isoprene complexes are described. These diene complexes are competent precatalysts for (i) the selective cross-[2+2]-cycloaddition of butadiene or (E)-piperylene with ethylene and α-olefins and (ii) the 1,4-hydrovinylation of isoprene with ethylene. In the former case, kinetic analysis implicated the diamagnetic η4-piperylene complex as the resting state prior to rate-determining oxidative cyclization. Variable temperature 1H NMR and EXSY experiments established that diene exchange from the diamagnetic, 18e complexes occurred rapidly in solution at ambient temperature through a dissociative mechanism. The solid-state structure of (Me(Et)PDI) Fe(η4-piperylene) (Me(Et)PDI=2,6-(2,6-Me2-C6H3N=CEt)2C5H3N) was determined by single-crystal X-ray diffraction and confirmed the s-trans coordination of the monosubstituted 1,3-diene. Possible relationships between ligand-controlled diene coordination geometry, metallacycle denticity, and chemoselectivity of iron-mediated cycloaddition reactions are discussed. (Figure presented.).

Original languageEnglish (US)
Pages (from-to)404-416
Number of pages13
JournalAdvanced Synthesis and Catalysis
Volume362
Issue number2
DOIs
StatePublished - Jan 23 2020

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry

Keywords

  • cycloaddition
  • diene ligands
  • iron
  • metallacycles

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