Issue 17, 2025

Understanding the factors governing the ammonia oxidation reaction by a mononuclear ruthenium complex

Abstract

Precise regulation of the active site of molecular catalysts is appealing because it could provide insights into the catalytic mechanism and possibly provide a new strategy for catalyst design. A ruthenium complex, [Ru(dppMe, COMe)(bipy)(Cl)] (CSU-3), containing –Me and –COMe substituted dipyridylpyrrole as a pincer ligand, was designed and synthesized. The CSU-3 complex featured a Cl ligand at the axial position as the active site for ammonia oxidation (AO), and is structurally analogous to AO catalyst [Ru(trpy)(dmabpy)(NH3)][PF6]2 (1) bearing a terpyridine ligand, but different from AO catalyst [Ru(dpp)(bipy)(NH3)] (CSU-2) containing unsubstituted dipyridylpyrrole as a hemilabile ligand with the active site at an equatorial position. To gain insight into the role of active-site and ligand regulation in the AO reaction, the structure and electrochemical properties of CSU-3 and its catalytic performance and mechanism for the AO reaction were comparably studied. Complex CSU-3 has good selective catalytic performance for the oxidation of ammonia to hydrazine with a turnover frequency (TOF) of 258.8 h−1 and N2H4 formation selectivity of 84.7% at Eapp of 1.0 V. The DFT calculations reveal that N2H4 as a dominant product is generated via an ammonia nucleophilic attack of ruthenium(IV)-imide to form N2H4 followed by N2H4-by-NH3 substitution.

Graphical abstract: Understanding the factors governing the ammonia oxidation reaction by a mononuclear ruthenium complex

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Article information

Article type
Edge Article
Submitted
10 Apr 2024
Accepted
03 Mar 2025
First published
19 Mar 2025
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2025,16, 7573-7578

Understanding the factors governing the ammonia oxidation reaction by a mononuclear ruthenium complex

G. Chen, X. Ding, P. He, T. Cheng, Y. Chen, J. Lin, X. Zhang, S. Zhao, N. Qiao and X. Yi, Chem. Sci., 2025, 16, 7573 DOI: 10.1039/D4SC02360A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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