Catalytic Ammonia Oxidation to Dinitrogen by Hydrogen Atom Abstraction. Issue 34 (11th June 2019)

• Record Type: Journal Article
• Authors: Bhattacharya, Papri; Heiden, Zachariah M.; Chambers, Geoffrey M.; Johnson, Samantha I.; Bullock, R. Morris; Mock, Michael T.
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 34(2019)
• Page Start: 11618
• Page End: 11624
• Publication Date: 2019-06-11
• Subjects: ammonia oxidation -- dinitrogen -- homogeneous catalysis -- radical reactions -- ruthenium; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201903221
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Catalysts for the oxidation of NH3 are critical for the utilization of NH3 as a large‐scale energy carrier. Molecular catalysts capable of oxidizing NH3 to N2 are rare. This report describes the use of [Cp*Ru(P t Bu 2 N Ph 2 )( 15 NH3 )][BAr F 4 ], (P t Bu 2 N Ph 2 =1, 5‐di(phenylaza)‐3, 7‐di(tert‐butylphospha)cyclooctane; Ar F =3, 5‐(CF3 )2 C6 H3 ), to catalytically oxidize NH3 to dinitrogen under ambient conditions. The cleavage of six N−H bonds and the formation of an N≡N bond was achieved by coupling H + and e − transfers as net hydrogen atom abstraction (HAA) steps using the 2, 4, 6‐tri‐ tert ‐butylphenoxyl radical ( t Bu3 ArO . ) as the H atom acceptor. Employing an excess of t Bu3 ArO . under 1 atm of NH3 gas at 23 °C resulted in up to ten turnovers. Nitrogen isotopic ( 15 N) labeling studies provide initial mechanistic information suggesting a monometallic pathway during the N⋅⋅⋅N bond‐forming step in the catalytic cycle. Abstract : Totally radical : A molecular Ru complex catalytically oxidizes NH3 to dinitrogen under ambient conditions. The cleavage of six N−H bonds and the formation of an N≡N bond was achieved by coupling H + and e − transfers as net hydrogen atom abstraction (HAA) steps using the 2, 4, 6‐tri‐ tert ‐butylphenoxyl radical ( t Bu3 ArO . ) as the H atom acceptor, resulting in up to 10 turnovers.