Bimetallic [Co/K] hydrogen evolution catalyst for electrochemical terminal C-H functionalization.

Discovering novel catalysts for hydrogen evolution reaction (HER) holds the potential to revolutionize the energy chemistry and unlock new tool for synthetic processes. Inspired by hydrogenases, we pair alkali metals with cobalt-Salen catalysts which allow the integration of naked base site into bimetallic HER catalysts. The incorporation of alkali metals (Na, K, Rb, Cs) significantly enhances HER activity. Among these, the [Co/K] system exhibits the highest HER catalytic efficiency (kobs ~ 31.4 s⁻¹), which is 9 times higher than the mononuclear analogue. Remarkably, this HER catalyst is repurposed for the terminal C(sp³)-H functionalization of N-allylimines with imine/aldehyde, a previously inaccessible transformation. Mechanistic studies reveal that the naked base site enables selective C-H activation via proton relay, overriding the inherent preference for Pinacol coupling. The electrochemical protocol features good functional group tolerance, and opens up a streamlined avenue for chiral pyrrolines, key precursors of the anti-cancer medicine Larotrectinib. More importantly, the alkali metal effect is rationalized through structural analysis, density functional theory (DFT) calculations, and control experiments.