Catalytic Nitrogen Fixation Using Molybdenum-Oxo Complexes Bearing NHC-Based PCP-Type Pincer Ligands Via...

Area of Science:

• Catalysis
• Sustainable Chemistry
• Inorganic Chemistry

Background:

• Developing water-compatible molecular catalysts is crucial for sustainable ammonia synthesis.
• Metal-oxo species are typically considered inactive byproducts in nitrogen fixation reactions.

Purpose of the Study:

• To investigate cationic molybdenum-oxo complexes with PCP-type pincer ligands as potential catalysts for ammonia formation.
• To challenge the conventional view of metal-oxo species as non-catalytic.

Main Methods:

• Synthesis of cationic molybdenum-oxo complexes.
• Catalytic ammonia synthesis using N2, SmI2, and water under ambient conditions.
• Stoichiometric reactions, electrochemical analysis, and DFT calculations to elucidate the catalytic mechanism.

Main Results:

• Molybdenum-oxo complexes effectively catalyzed ammonia formation, yielding up to 22,000 equivalents.
• The active species were identified as molybdenum-nitride complexes, formed in situ from the oxo precursors.
• The oxo-to-nitride conversion mechanism involves oxygen abstraction or protonation/reduction followed by N2 cleavage.

Conclusions:

• Molybdenum-oxo complexes are viable and versatile catalyst precursors, not dead-end species.
• This work opens new avenues for designing catalysts for sustainable nitrogen fixation.
• The findings contribute to the development of environmentally friendly ammonia synthesis processes.