Nanocatalysts Based on Ni Nanoparticles in Functionalized Ionic Liquids for Chemoselective Hydrogenation and Transfer Hydrogenation of α,β-unsaturated Carbonyl Compounds

For the development of catalytically active and selective Ni nanoparticle (NP) catalysts both the choice of the synthesis method and the selection of stabilizer are key parameters. A series of Ni NPs were synthesized in various ionic liquids (Ni/ILs) and applied as catalysts for the chemoselective reduction of 2-cyclohexen-1-one (1), as a representative of the group of α,β-unsaturated carbonyl compounds with industrial relevance. The Ni/ILs systems were found to be efficient catalysts for the selective hydrogenation of 1 to cyclohexanone (2) under quite mild reaction conditions (130-170 °C, 10 bar H₂, 1/Ni molar ratio of 100/1), achieving high conversions in a short reaction time (1 h). The oxidized counterparts (Ni-NiO/ILs) showed to be active for the selective catalytic transfer hydrogenation (CTH) of 1 to 2-cyclohexen-1-ol (3) with 2-propanol, also under mild reaction conditions (150 °C, 48 h, 1/Ni ratio of 50/1).