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doi:10.1016/j.molcata.2006.12.003 
Copyright © 2006 Elsevier B.V. All rights reserved.
N-heterocyclic carbene–palladium complex immobilized on silica nanoparticles Recyclable catalyst for high yield Suzuki and Heck coupling reactions under mild conditions
Received 30 November 2006;
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Abstract
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.
Graphical abstract
N-heterocyclic carbene–palladium (NHC–Pd) complexes immobilized on 10 nm silica nanoparticles were synthesized. 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 and Heck coupling reactions. The nano-sized particles can be easily recovered and repeatedly reused without loss of activity.
Keywords: Palladium catalyst; Silica nanoparticles; Suzuki coupling; Heck coupling
Article Outline
- 1. Introduction
- 2. Experimental
- 2.1. Materials and instrumentation
- 2.2. Preparation of 1-decyl-3-(triethoxysilyl propyl) imidazolium salts immobilized on silica nanoparticles
- 2.2.1. Synthesis of 1-decyl-3-(triethoxysilyl propyl) imidazolium chloride
- 2.2.2. NHC precursor covalently bonded to silica nanoparticles
- 2.2.3. Preparation of silica supported N-heterocyclic carbene–Pd complex
- 2.3. General procedure for Suzuki coupling
- 2.4. General procedure for Heck coupling
- 2.5. Procedure for recycling of the catalyst
- 3. Results and discussion
- 3.1. Preparation of 1-decyl-3-(triethoxysilyl propyl) imidazolium salts immobilized on silica nanoparticles
- 3.2. In situ preparation of silica supported N-heterocyclic carbene–Pd complex
- 3.3. Heterogeneous Suzuki cross-coupling reaction
- 3.4. Heterogeneous Heck cross-coupling reaction
- 3.5. Reusability of silica supported catalyst
- 4. Conclusion
- Acknowledgements
- References
