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.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry