Iron Phosphine Catalyzed Cross-Coupling of Tetraorganoborates and Related Group 13 Nucleophiles with Alkyl Halides

Robin B. Bedford*, Peter B. Brenner, Emma Carter, Jamie Clifton, Paul M. Cogswell, Nicholas J. Gower, Mairi F. Haddow, Jeremy N. Harvey, Jeffrey A. Kehl, Damien M. Murphy, Emily C. Neeve, Michael L. Neidig, Joshua Nunn, Benjamin E R Snyder, Joseph Taylor

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

62 Citations (Scopus)

Abstract

Iron phosphine complexes prove to be good precatalysts for the cross-coupling of alkyl, benzyl, and allyl halides with not only aryl triorganoborate salts but also related aluminum-, gallium-, indium-, and thallium-based nucleophiles. Mechanistic studies revealed that while Fe(I) can be accessed on catalytically relevant time scales, lower average oxidation states are not formed fast enough to be relevant to catalysis. EPR spectroscopic studies reveal the presence of bis(diphosphine)iron(I) complexes in representative catalytic reactions and related processes with a range of group 13 nucleophiles. Isolated examples were studied by Mossbauer spectroscopy and single-crystal X-ray structural analysis, while the electronic structure was probed by dispersion-corrected B3LYP DFT calculations. An EPR study on an iron system with a bulky diphosphine ligand revealed the presence of an S = 1/2 species consistent with the formation of a mono(diphosphine)iron(I) species with inequivalent phosphine donor environments. DFT analysis of model complexes allowed us to rule out a T-shaped Fe(I) structure, as this is predicted to be high spin.

Original languageEnglish
Pages (from-to)5767-5780
Number of pages14
JournalOrganometallics
Volume33
Issue number20
DOIs
Publication statusPublished - 27 Oct 2014

Structured keywords

  • BCS and TECS CDTs

Keywords

  • ARYL-GRIGNARD-REAGENTS
  • BEARING BETA-HYDROGENS
  • ALKENYL HALIDES
  • STEREOSELECTIVE-SYNTHESIS
  • HETEROARYL HALIDES
  • ACYL CHLORIDES
  • BENZYL HALIDES
  • TRISUBSTITUTED OLEFINS
  • ALLYLIC PHOSPHATES
  • CARBENE CATALYSTS

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