Direct Observation of Transmetalation from a Neutral Boronate Ester to a Pyridine(diimine) Iron Alkoxide

Paul O. Peterson, Stephan M. Rummelt, Bradley M. Wile, S. Chantal E. Stieber, Hongyu Zhong, Paul J. Chirik

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Transmetalation of the neutral boronate esters, (2-benzofuranyl)BPin and (2-benzofuranyl)BNeo (Pin = pinacolato, Neo = neopentylglycolato), to a representative pyridine(diimine) iron alkoxide complex, (iPrPDI)FeOEt (iPrPDI = 2,6-(2,6-iPr2-C6H3Nâ• CMe)2C5H3N; R = Me, Et, SiMe3), to yield the corresponding iron benzofuranyl derivative was studied. Synthesis of the requisite iron alkoxide complexes was accomplished either by salt metathesis between (iPrPDI)FeCl and NaOR (R = Me, Et, SiMe3) or by protonation of the iron alkyl, (iPrPDI)FeCH2SiMe3, by the free alcohol R′OH (R′ = Me, Et). A combination of magnetic measurements, X-ray diffraction, NMR, and Mössbauer spectroscopies and DFT calculations identified each (iPrPDI)FeOR compound as an essentially planar, high-spin, S = 3/2 compound where the iron is engaged in antiferromagnetic coupling with a radical anion on the chelate (STotal = 3/2; SFe = 2, SPDI =-1/2). The resulting iron benzofuranyl product, (iPrPDI)Fe(2-benzofuranyl), was characterized by X-ray diffraction and in combination with magnetic measurements, spectroscopic and computational data, was identified as an overall S = 1/2 compound, demonstrating that a net spin-state change accompanies transmetalation (SFe = 1, SPDI =-1/2). These findings may be relevant to further development of iron-catalyzed Suzuki-Miyaura cross-coupling with neutral boronate esters and alkoxide bases.

Original languageEnglish (US)
Pages (from-to)201-205
Number of pages5
JournalOrganometallics
Volume39
Issue number1
DOIs
StatePublished - Jan 13 2020

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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