Proximal Ir-Ir Cooperativity for Reprogramming the CO2-to-DMF Hydrogenation Pathway.

The hydrogenation of CO2 to N,N-dimethylformamide (DMF) with dimethylamine requires the concerted transformation of three distinct substrates, a fundamental kinetic challenge that mononuclear catalysts can only address through high-barrier, sequential steps. Herein, we demonstrate a ligand-enabled proximity strategy in binuclear Cp*Ir(III) complexes, wherein the spatial confinement of two metal centers facilitates the concerted activation of multiple substrates. The optimized binuclear architecture, equipped with strategically positioned ‒OH pendants, transforms the rate-limiting termolecular collision into a kinetically favorable, low-barrier pathway. This electronic and spatial cooperativity culminates in a turnover number of 1 540 000, placing the catalyst among the most efficient molecular systems reported for DMF production with selectivity approaching quantitative (> 99%). Integrated computational and spectroscopic studies reveal that the dual-Ir framework mitigates the entropic penalty inherent to termolecular processes, while the hydroxyl functionality polarizes the Ir‒H bond to promote H2 heterolysis and CO2 insertion. In situ NMR and infrared spectroscopy directly identify the key Ir-hydride and Ir-formate intermediates, providing experimental validation of the computationally predicted low-barrier pathway. These findings establish for the first time how multimetallic cooperativity and secondary coordination sphere effects operate in concert to bypass the intrinsic kinetic limitations of single-site catalysts.