Catalytic Nitrogen-to-Ammonia Conversion by Osmium and Ruthenium Complexes
Javier Fajardo1, Jonas C Peters1
1Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Ruthenium (Ru) and Osmium (Os) complexes now catalyze nitrogen fixation (N2RR), converting N2 to ammonia (NH3). The Osmium system is most active, yielding over 120 equivalents of NH3, with a hydrazido intermediate proposed.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Nitrogen Fixation
Background:
- Ruthenium (Ru) and Osmium (Os) complexes are crucial in transition metal dinitrogen chemistry.
- However, they have not previously mediated catalytic nitrogen fixation (N2-to-ammonia conversion, N2RR).
- M-NxHy complexes have not been derived from protonation of M-N2 precursors.
Purpose of the Study:
- To delineate factors influencing N2RR catalysis.
- To report on isostructural tris(phosphino)silyl Ru and Os complexes for N2RR.
- To compare catalytic activities with an isostructural iron (Fe) complex.
Main Methods:
- Synthesis of isostructural tris(phosphino)silyl Ru, Os, and Fe complexes.
- Catalytic N2RR experiments using Cp*2Co as reductant and [H2NPh2][OTf] as acid source.
- Structural characterization of intermediates, including protonation of Os-N2- to an Os=NNH2+ hydrazido species.
- Characterization of Os hydrides formed during catalysis.
Main Results:
- The Osmium system demonstrated the highest activity, liberating over 120 equivalents of ammonia (NH3) per Os center in a single batch.
- Isostructural Ru and Fe complexes generated minimal NH3 under identical conditions.
- Protonation of the Os-N2- complex yielded a structurally characterized Os=NNH2+ hydrazido species.
- Inactive Os hydrides were identified as catalytic byproducts.
Conclusions:
- Isostructural tris(phosphino)silyl Ru and Os complexes mediate catalytic N2RR, with Os being the most active.
- The Os=NNH2+ hydrazido species is a plausible intermediate in the catalytic cycle.
- This work provides insights into factors governing N2RR catalysis using Ru and Os complexes.
More Related Videos
10:51The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
08:40Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production
Published on: December 6, 2021
Related Concept Videos
Preparation of Amines: Reduction of Oximes and Nitro Compounds
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
Catalysis
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
2° Amines to N-Nitrosamines: Reaction with NaNO2
Electrophilic Aromatic Substitution: Nitration of Benzene
