Bimetallic Cooperativity in Proton Reduction with an Amido‐Bridged Cobalt Catalyst

The bimetallic catalyst [Co II 2 (L 1 )(bpy) 2 ]ClO 4 ( 1 ), in which L 1 is an [NN′ 2 O 2 ] fused ligand, efficiently reduced H + to H 2 in CH 3 CN in the presence of 100 equiv of HOAc with a turnover number of 18 and a Faradaic efficiency of 94 % after 3 h of bulk electrolysis at −1.6 V (vs. Ag/AgCl). This observation allowed the proposal that this bimetallic cooperativity is associated with distance, angle, and orbital alignment of the two Co centers, as promoted by the unique Co−N amido −Co environment offered by L 1 . Experimental results revealed that the parent [Co II Co II ] complex undergoes two successive metal‐based 1 e − reductions to generate the catalytically active species [Co I Co I ], and DFT calculations suggested that addition of a proton to one Co I triggers a cooperative 1 e − transfer by each of these Co I centers. This 2 e − transfer is an alternative route to generate a more reactive [Co II (Co II −H − )] hydride, thus avoiding the Co III −H − required in monometallic species. This [Co II (Co II −H − )] species then accepts another H + to release H 2 .