Reversible CO2 Hydrogenation, Neutron Crystallography, and Hydride Reactivity of a Triiridium Heptahydride Complex
Year: 2025
Type: article
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).
Authors: Valeriy Cherepakhin, Van K. Do, Anthony J. Chavez, Jacob Kelber, Ryan A. Klein, Eric Novak, Yongqiang Cheng, Xiaoping Wang, Craig M. Brown, Travis J. Williams
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, National Institutes of Health, National Institute of Standards and Technology, Office of Science, Office of Energy Efficiency and Renewable Energy, Division of Chemistry, Hydrogen and Fuel Cell Technologies Office, Oak Ridge National Laboratory, National Renewable Energy Laboratory
Awards: Collaborative Research: Acquisition of a 400 MHz NMR at the University of Southern California, G1638050999, G2268476748, G2278757305, G3306068231, G357224917, G3634295717, G3815375274, MRI: Acquisition of a 600 Mhz NMR Spectrometer at the University of Southern California, G5366184946, MRI: Acquisition of an X-ray Diffractometer at the University of Southern California, REU Site: Snapshots of Chemistry -- Visualization of Processes at the Molecular Level, G6796889085, G8849833124
OpenAlex ID: W4408245570