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Vanadium-Catalyzed Dinitrogen Reduction to Ammonia via a [V]═NNH2 Intermediate
Wenshuang Huang1, Ling-Ya Peng2, Jiayu Zhang3
1College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
Journal of the American Chemical Society
|January 3, 2023
Summary
Researchers developed a novel vanadium catalyst for nitrogen (N2) fixation, converting N2 into ammonia (NH3). This study identifies a key metal hydrazido intermediate, advancing understanding of nitrogen reduction mechanisms.
Area of Science:
- Inorganic Chemistry
- Catalysis
- Bioinorganic Chemistry
Background:
- Nitrogen (N2) fixation to ammonia (NH3) is crucial but challenging for synthetic catalysts.
- Vanadium's role in biological N2 fixation is known, yet well-defined catalytic vanadium complexes are rare.
- A V(NH) intermediate in N2 reduction remains elusive.
Purpose of the Study:
- To report a novel divanadium complex for N2 reduction.
- To characterize a key intermediate in the catalytic cycle.
- To elucidate the N2 reduction mechanism using experimental and theoretical methods.
Main Methods:
- Synthesis and characterization of a dinitrogen-bridged divanadium complex.
- Low-temperature protonation and reduction studies.
- Density Functional Theory (DFT) calculations.
- Isotopic labeling studies using 15N2.
Main Results:
- A dinitrogen-bridged divanadium complex catalyzed N2 to NH3 and N2H4 reduction.
- The first structurally characterized neutral metal hydrazido(2-) species, [V]=NNH2, was obtained.
- [V]=NNH2 mediated 15N2 conversion to 15NH3, confirming its role as a catalytic intermediate.
- DFT calculations revealed a high N-H bond dissociation free energy (BDFE N-H) of 59.1 kcal/mol for the hydrazido complex.
- Experimental and theoretical data suggest a distal pathway for NH3 liberation.
Conclusions:
- The study presents a novel vanadium catalyst for N2 reduction.
- A key metal hydrazido intermediate was identified and characterized.
- Findings offer insights into N2 reduction mechanisms, relevant to FeV nitrogenase.
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