A Chatt-Type Catalyst with One Coordination Site for Dinitrogen Reduction to Ammonia

Area of Science:

• Organometallic Chemistry
• Catalysis
• Nitrogen Fixation

Background:

• Nitrogen (N₂) is abundant but inert, requiring significant energy for conversion to ammonia.
• Developing efficient catalysts for N₂ reduction is crucial for sustainable ammonia production.

Purpose of the Study:

• To present the first Chatt-type complex capable of catalytically converting N₂ to ammonia.
• To investigate the role of ligand structure and complex topology in N₂ activation and reduction.

Main Methods:

• Synthesis and characterization of a novel molybdenum-dinitrogen complex with a pentapod ligand.
• Catalytic testing using samarium diiodide (SmI₂) as reductant and water as proton source.
• Spectroscopic and structural analysis to understand reaction mechanisms.

Main Results:

• The title complex [Mo(N₂)(P₂^MePP₂^Ph)] catalytically converts N₂ to 26 equivalents of ammonia.
• Analogous complexes with different phosphine ligands were inactive, highlighting the importance of the pentapod ligand.
• A related hydrazido(2-) complex was also catalytically active, supporting a mononuclear pathway.

Conclusions:

• The pentapod ligand P₂^MePP₂^Ph strongly activates N₂, enabling efficient catalytic ammonia synthesis.
• The catalytic cycle proceeds via a mononuclear pathway, avoiding dimerization.
• Proton-coupled electron transfer (PCET) mechanisms are relevant to this reactive scheme.