Catalytic Nitrene Transfer by an Fe^IV -Imido Complex Generated by a Comproportionation Process.

Area of Science:

• Organometallic Chemistry
• Catalysis
• Reaction Mechanisms

Background:

• Nitrene transfer reactions are vital for C-H amination but lack detailed mechanistic understanding.
• Nitrene generation mechanisms are often assumed without definitive evidence.
• Iron complexes are increasingly explored as catalysts for nitrene transfer.

Purpose of the Study:

• To elucidate the mechanism of nitrene generation and transfer from iron precursors.
• To identify the catalytically active species in tosyl nitrene transfer reactions.
• To compare nitrene generation pathways from Fe(II) and Fe(III) tetracarbene macrocycle complexes.

Main Methods:

• Catalytic nitrene transfer reactions with various hydrocarbon substrates.
• Spectroscopic characterization including UV-visible, Mössbauer, and EPR spectroscopy.
• Electrospray ionization mass spectrometry (ESI-MS) and Density Functional Theory (DFT) calculations.

Main Results:

• Identified an Fe(IV) tosylimido species as the active catalyst, irrespective of the Fe(II) or Fe(III) precursor.
• Established that Fe(IV) tosylimido formation from Fe(II) proceeds via oxidative addition.
• Uncovered an unprecedented pathway from Fe(III) involving an Fe(V) intermediate and comproportionation to form the active Fe(IV) species.

Conclusions:

• The catalytically active species in tosyl nitrene transfer is an Fe(IV) tosylimido complex.
• Distinct mechanistic pathways for nitrene generation exist from Fe(II) and Fe(III) precursors.
• This work provides crucial mechanistic insights into iron-catalyzed nitrene transfer reactions.