Electrocatalytic H 2 Generation from Water Relying on Cooperative Ligand Electron Transfer in “PN 3 P” Pincer‐Supported Ni II Complexes

Water is the most sustainable source for H 2 production, and the efficient electrocatalytic production of H 2 from mixed water/acetonitrile solutions by using two new air‐stable nickel(II) pincer complexes, [Ni(κ 3 ‐2,6‐{Ph 2 PNR} 2 (NC 5 H 3 )Br 2 ] (R=H I , Me II ) is reported. Hydrogen generation from H 2 O/CH 3 CN solutions is initiated at −2 V against Fc +/0 , and bulk electrocatalysis studies showed that the catalyst functions with an excellent Faradaic efficiency and a turnover frequency of 160 s −1 . A DFT computational investigation of the reduction behavior of I and II revealed a correlation of H 2 formation with charge donation from electrons originating in a reduced ligand‐localized orbital. As a result, these catalysts are proposed to proceed by a novel mechanism involving electron/proton transfer between a Ni 0I species bonded to an anionic PN 3 P ligand (“L − /Ni 0I ”) and a Ni I ‐hydride (“Ni−H”). Furthermore, these catalysts are able to reduce phenol and acetic acid, more active proton sources, at lower potentials that correlate with the substrate p K a .