Electrocatalytic Transfer Hydrogenation of 1-Octene with [( tBu PCP)Ir(H)(Cl)] and Water

Electrocatalytic hydrogenation of 1-octene as non-activated model substrate with neutral water as H-donor is reported, using [( PCP)Ir(H)(Cl)] (1) as the catalyst, to form octane with high faradaic efficiency (FE) of 96 % and a k of 87 s . Cyclic voltammetry with 1 revealed that two subsequent reductions trigger the elimination of Cl and afford the highly reactive anionic Ir(I) hydride complex [( PCP)Ir(H)] (2), a previously merely proposed intermediate for which we now report first experimental data by mass spectrometry. In absence of alkene, the stoichiometric electrolysis of 1 in THF with water selectively affords the Ir(III) dihydride complex [( PCP)Ir(H) ] (3) in 88 % FE from the reaction of 2 with H O. Complex 3 then hydrogenates the alkene in classical fashion. The presented electro-hydrogenation works with extremely high FE, because the iridium hydrides are water stable, which prevents H formation. Even in strongly alkaline conditions (Bu NOH added), the electro-hydrogenation of 1-octene with 1 also proceeds cleanly (89 % FE), suggesting a highly robust process that may rely on H O activation, reminiscent to transfer hydrogenation pathways, instead of classical H reduction. DFT calculations confirmed oxidative addition of H O as a key step in this context.