Rapid Iron(III)-Fluoride-Mediated Hydrogen Atom Transfer

摘要

We anticipate high-valent metal-fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H-F bond (in the product) that drives HAT oxidation. We prepared a dimeric Fe-III(F)-F-Fe-III(F) complex (1) by reacting Fe-II(NCCH3)(2)(TPA)(ClO4)(2) (TPA=tris(2-pyridylmethyl)amine) with difluoro(phenyl)-lambda(3)-iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Bronsted acids to yield a monomeric Fe-III(TPA)(F)(X)(+) complex (2) where X=F/OTf. 1 and 2 were characterized using NMR, EPR, UV/Vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive Fe-III reagent for oxidative C-H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive Fe-III and Fe-IV oxidants.