Reversible CO2 Hydrogenation, Neutron Crystallography, and Hydride Reactivity of a Triiridium Heptahydride Complex

Published

April 1, 2025

Author(s)

Valeriy Cherepakhin, Van K. Do, Anthony J. Chavez, Jacob Kelber, Ryan Klein, Eric Novak, Yongqiang Cheng, Xiaoping Wang, Craig Brown, Travis J. Williams

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 [AgIr2H4(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).

Citation

Angewandte Chemie International Edition

Volume

64

Issue

21

Pub Type

Journals

Download Paper

https://doi.org/10.1002/anie.202501943

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Keywords

metal hydrides, neutron crystallography, inelastic neutron scattering, hydrogen carrier, CO2 hydrogenation, formic acid dehydrogenation

Citation

Cherepakhin, V. , Do, V. , Chavez, A. , Kelber, J. , Klein, R. , Novak, E. , Cheng, Y. , Wang, X. , Brown, C. and Williams, T. (2025), Reversible CO2 Hydrogenation, Neutron Crystallography, and Hydride Reactivity of a Triiridium Heptahydride Complex, Angewandte Chemie International Edition, [online], https://doi.org/10.1002/anie.202501943, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957438 (Accessed July 12, 2025)