Hydrocarbon Oxidation by an Exposed, Multiply Bonded Iron(III) Oxo Complex

Area of Science:

• Bioinorganic Chemistry
• Organometallic Chemistry
• Oxidation Catalysis

Background:

• The iron oxo unit ([Fe=O]) is a key intermediate in biological oxidation.
• Higher oxidation states of iron oxo units are well-understood.
• The least-oxidized form, iron(III) oxo ([Fe^III=O]⁺), remains less characterized.

Purpose of the Study:

• To structurally, spectroscopically, and computationally characterize a novel iron(III) oxo complex.
• To investigate the electronic structure and bonding of the iron-oxygen moiety.
• To evaluate the catalytic activity of the complex in hydrocarbon oxidation reactions.

Main Methods:

• Synthesis and isolation of the PhB(AdIm)₃Fe=O complex.
• Single-crystal X-ray diffraction for structural determination.
• Spectroscopic analyses (e.g., UV-Vis, Mössbauer) and Density Functional Theory (DFT) calculations for electronic structure investigation.
• Hydrocarbon oxidation reaction studies.

Main Results:

• A thermally stable iron(III) oxo complex, PhB(AdIm)₃Fe=O, was successfully synthesized and characterized.
• An unusually short Fe-O bond length was observed, indicative of significant iron-oxygen multiple bond character.
• Electronic structure calculations confirmed the presence of multiple bonding and the iron(III) oxidation state.
• The complex demonstrated catalytic activity in hydrocarbon oxidation, enabling C-O bond formation and dehydrogenation.

Conclusions:

• PhB(AdIm)₃Fe=O represents a genuine iron(III) oxo species with significant Fe-O multiple bond character.
• The characterized complex serves as a valuable model for understanding biological oxidation intermediates.
• This stable iron(III) oxo complex has potential applications in catalytic oxidation processes.