N-heterocyclic carbene-palladium complex immobilized on silica nanoparticles. Recyclable catalyst for high yield Suzuki and Heck coupling reactions under mild conditions

N-heterocyclic carbene-palladium (NHC-Pd) complexes immobilized on ∼10 nm silica nanoparticles were synthesized. Because of the very high surface area and small size, these nanoparticles remain suspended in a variety of solvents with the catalyst sites readily accessible to the reactants. The catalysts showed excellent activity towards Suzuki coupling reaction of different aryl iodides and bromides with phenyl boronic acid using isopropanol: H₂O as solvent. They were also effective for Heck coupling. The nano-sized particles can be easily recovered and repeatedly reused without loss of activity.