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

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Oxidation Chemistry

Background:

• High-valent metal-fluoride species are predicted to be effective hydrogen atom transfer (HAT) oxidants due to the strong driving force from the H-F bond formation.
• The development of novel oxidants is crucial for advancing catalytic C-H activation processes.

Purpose of the Study:

• To synthesize and characterize novel high-valent iron-fluoride complexes.
• To investigate the oxidative capabilities of these complexes in hydrogen atom transfer (HAT) reactions.
• To explore the activation of these complexes using Lewis or Brønsted acids.

Main Methods:

• Synthesis of a dimeric Fe(III)-F-Fe(III) complex (1) from a Fe(II) precursor and difluoroiodobenzene.
• Activation of complex 1 with Lewis or Brønsted acids to form monomeric Fe(III) complexes (2).
• Characterization of complexes 1 and 2 using various spectroscopic techniques (NMR, EPR, UV/Vis, FT-IR) and mass spectrometry.

Main Results:

• A dimeric Fe(III)-F-Fe(III) complex (1) was successfully prepared.
• Complex 1 exhibited sluggish oxidation activity but was readily activated by acids.
• The activated monomeric Fe(III) complex (2) demonstrated high reactivity in oxidative C-H activation, comparable to potent Fe(III) and Fe(IV) oxidants.

Conclusions:

• High-valent iron-fluoride complexes can serve as effective hydrogen atom transfer (HAT) oxidants.
• Acid activation is a viable strategy to significantly enhance the reactivity of these iron-fluoride species.
• The activated Fe(III) complexes represent a new class of potent reagents for oxidative C-H activation.