Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis.

Autor: Liu L; Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA.; Current address: College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, P. R. China., Johnson SI; Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA., Appel AM; Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA., Bullock RM; Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA.
Jazyk: angličtina
Zdroj: Angewandte Chemie (International ed. in English) [Angew Chem Int Ed Engl] 2024 Oct 07; Vol. 63 (41), pp. e202402635. Date of Electronic Publication: 2024 Sep 05.
DOI: 10.1002/anie.202402635
Abstrakt: Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon-neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth-abundant transition metal complex, trans-[LFe II (MeCN) 2 ][PF 6 ] 2 , where L is a macrocyclic ligand bearing four N-heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N 2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p-MeOC 6 H 4 ) 3 N exhibited a catalytic half-wave potential (E cat/2 ) of 0.18 V vs [Cp 2 Fe] +/0 in MeCN, and achieved 9.3 turnovers of N 2 at an applied potential of 0.20 V vs [Cp 2 Fe] +/0 at -20 °C in controlled-potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFe IV (NH 2 ) 2 ] 2+ , and thereafter bimetallic coupling to form an N-N bond.
(© 2024 Battelle Memorial Institute. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)
Databáze: MEDLINE
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