Unusual Catalytic Hydrogenation Caused by Photoinduced Solid Frustrated Lewis Pairs

Most homogeneously FLP-catalyzed hydrogenation reactions that follow cleavage of H2 occur via protonation of substrates followed by hydride transfer. This order of activated H-transfer unavoidably limits the application scope of currently FLP-catalyzed hydrogenation to nucleophilic substrates. Herein, we report an unusual inverse H-transfer order in which photoinduced solid In2O3-FLPs catalyze the hydrogenated dehalogenation of aryl halides with H2. After the generation of active FLPs of In-OH+ and In-[Ov]H- via H2 splitting on In2O3 surface upon irradiation, a series of aryl halides were readily activated and initiated at the In-[Ov]H- sites and then dehalogenated with high yields. By combining this work with detailed studies on H/D kinetic isotope effects and activation energies of hydrogenated dehalogenation, we demonstrate that initial hydride transfer mediated by photoinduced solid FLPs is more effective than common proton transfer to initiate hydrogenation of these substrates.