Enhanced Rate of Arene Hydrogenation with Imidazolium Functionalized Bipyridine Stabilized Rhodium Nanoparticle Catalysts

The imidazolium functionalized bipyridine compounds, {4,4′-bis[7-(2,3-dimethylimidazolium)heptyl]-2,2′-bipyridine}2+ ([BIHB]2+) and {4,4′-bis[(1,2-dimethylimidazolium)methyl]-2,2′-bipyridine}2+ ([BIMB]2+), were prepared and used as Rh nanoparticle stabilizers. The dispersed Rh nanoparticles were used as catalysts in the biphasic hydrogenation of various arene substrates. The catalytic activity was strongly influenced by the stabilizer employed and followed the trend [BIHB]2+ > bipy > [BIMB]2+. The steric and electronic characteristics of the imidazolium functionalized bipyridine ligands were assessed via the synthesis of rhenium carbonyl complexes, which facilitated the rationalization of the catalytic properties of the nanoparticles.