Metal-Organic Framework Stabilizes a Low-Coordinate Iridium Complex for Catalytic Methane Borylation

Area of Science:

• Catalysis
• Materials Science
• Organic Chemistry

Background:

• Methane conversion to fine chemicals via catalytic borylation is promising but requires improved catalyst activity.
• Existing iridium (Ir) complexes with phenanthroline and diphosphine ligands show limited efficiency.

Purpose of the Study:

• To develop highly active catalysts for methane borylation using metal-organic frameworks (MOFs).
• To stabilize low-coordinate iridium complexes for enhanced catalytic performance.

Main Methods:

• Synthesis and application of a mono(phosphine)-iridium based MOF (Zr-P1-Ir).
• Methane borylation reaction studies at 110 °C.
• Density functional theory (DFT) calculations to elucidate reaction mechanisms.

Main Results:

• The Zr-P1-Ir MOF catalyst achieved a turnover number of 127 for methane borylation, yielding CH3Bpin.
• DFT calculations revealed a reduced activation barrier for methane oxidative addition due to stabilized four-coordinate Ir complexes.
• The MOF strategy avoided sterically hindered seven-coordinate intermediates, unlike other Ir catalysts.

Conclusions:

• MOFs effectively stabilize low-coordinate iridium catalysts, enabling highly active methane borylation.
• This approach offers a unique strategy to overcome activation barriers for inert substrates.
• MOF-based catalyst design shows significant potential for challenging catalytic transformations.