Iron(III)-Mediated C-H Alkylation: One-Electron Differentiation Increases Activity and Chemoselectivity

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• C-H functionalization is a key transformation in organic synthesis.
• Iron complexes offer a sustainable alternative to precious metal catalysts.
• Previous iron catalysts showed limitations in reactivity and selectivity.

Purpose of the Study:

• To develop novel iron(III) catalysts for C-H functionalization.
• To investigate the mechanism of iron-mediated C-H activation and alkylation.
• To compare the performance of iron(III) catalysts with iron(II) counterparts.

Main Methods:

• Synthesis of iron(III) complexes with bis(phosphine) ligands.
• C-H activation and alkylation reactions using various arene derivatives.
• Kinetic studies, deuterium labeling, kinetic isotope effect, and computational modeling.

Main Results:

• A cationic iron(III) metallacycle was synthesized and characterized.
• The iron(III) complex mediated selective *ortho*-alkylation of arenes with diverse directing groups.
• Iron(III) catalysts exhibited superior reactivity and selectivity compared to iron(II) analogs.

Conclusions:

• Iron(III) complexes are effective catalysts for C-H functionalization.
• The mechanism involves reversible C-H activation followed by reductive elimination.
• Catalyst design principles can enhance selectivity and substrate scope in C-H functionalization.