Remote C–H bond cooperation strategy enabled silver catalyzed borrowing hydrogen reactions†

Abstract

Metal–ligand cooperation (MLC) is an essential strategy in transition metal catalysis. Traditional NH-based and OH-based MLC catalysts, as well as the later developed (de)aromatization strategy, have been widely applied in atom-economic borrowing hydrogen/hydrogen auto-transfer (BH/HA) reactions. However, these conventional MLC approaches are challenging for low-coordination and low-activity coinage metal complexes, arising from the instability during (de)protonation on the coordination atom, the constraint in linear coordination, and possible poisoning due to extra functional sites. Herein, we demonstrate a remote C–H bond cooperation strategy that enables the unprecedented homogeneous Ag(I)-catalyzed BH/HA reaction. The covalent C–H bifunctional site well facilitates (de)hydrogenation, especially under the low coordination circumstances of d¹⁰ Ag(I). The strong electron-donating bis-N-heterocyclic carbene (NHC) ligand stabilizes the silver–hydride and stimulates the hydride activity on the trans-position of ligands. Mechanistic studies implicate the plausible remote assistance of the dissociative NHC arm in facilitating BH/HA reactions. Our findings emphasize the potential of the remote C–H bond cooperation strategy for low coordination metals in catalyzing BH/HA reactions and broadening MLC catalysts to d¹⁰ coinage metals.