Reversible CO2 Hydrogenation, Neutron Crystallography, and Hydride Reactivity of a Triiridium Heptahydride Complex
Date
2025-04-01
Journal Title
Journal ISSN
Volume Title
Publisher
Angewandte Chemie International Edition
Abstract
The authors report the structure, reactivity, and catalytic utility of a triiridium complex, [Ir3H6(μ3-H)(PN)3]2+ (2-H, PN = (2-pyridyl)CH2PBut2). Despite its unusual stability to unsaturated organics, electrophiles, and even CF3SO3D, they find that complex 2-H catalyzes hydrogenation of CO2 to formate (TONIr = 9600) and reverse formic acid dehydrogenation (TONIr = 54 400). The hydrogenation operates via a reactive intermediate [Ir3H4(μ-H)4(PN)3]+ (5). Neutron crystallography and DFT-supported neutron vibrational spectroscopy of 2-H reveal Ir─H bond lengths and elucidate the vibration modes within the Ir3H7 core. Stoichiometric oxidation of 2-H produces four classes of iridium complexes of varied nuclearity and hydride structure: tetra- and pentanuclear clusters [Ir3H6(μ3-AuPPh3)(PN)3]2+ (2-Au) and [Ag{Ir2H4(μ-OAc)(PN)2}2]3+ (6) are generated using AuPPh3+ and AgOAc, respectively. Further oxidation to class [Ir2H3(μ-X)2(PN)2]+ is possible with AgOAc, Hg(OAc)2, or I2. Finally, a TEMPO/HCl system completely oxidizes the hydrides and gives [Ir2Cl4(μ-Cl)2(PN)2] (11).
Graphical Abstract available at: https://doi.org/10.1002/anie.202501943
A novel triiridium heptahydride cluster catalyzes reversible CO2 hydrogenation. Foundational structural and reactivity studies that combine neutron crystallography and spectroscopy, electrochemistry, synthetic studies, and kinetics uncover previously elusive metal–metal cooperative reactivity that enables a unique approach to functionalizing CO2.
Description
This is the peer reviewed version of the following article: V. Cherepakhin, V. K. Do, A. J. Chavez, J. Kelber, R. A. Klein, E. Novak, Y. Cheng, X. Wang, C. M. Brown, T. J. Williams, Angew. Chem. Int. Ed. 2025, e202501943. https://doi.org/10.1002/anie.202501943, which has been published in final form at https://doi.org/10.1002/anie.202501943. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.
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Keywords
catalysis, formate, heterometallic cluster, metal hydride, oxidation
Citation
V. Cherepakhin, V. K. Do, A. J. Chavez, J. Kelber, R. A. Klein, E. Novak, Y. Cheng, X. Wang, C. M. Brown, T. J. Williams, Angew. Chem. Int. Ed. 2025, e202501943. https://doi.org/10.1002/anie.202501943