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

We 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, we find that complex 2-H catalyzes hydrogenation of CO2 to formate (TONIr = 9,600) and reverse formic acid dehydrogenation (TONIr = 54,400). The hydrogenation operates via a reactive intermediate [Ir3H4(µ-H)4(PN)3]+ (5).