Immobilization on a Nanomagnetic Co/C Surface Using ROM Polymerization: Generation of a Hybrid Material as Support for a Recyclable Palladium Catalyst

• Published in: Advanced functional materials 2010-12, Vol.20 (24), p.4323-4328
• Main Authors: Schätz, Alexander, Long, Toby R., Grass, Robert N., Stark, Wendelin J., Hanson, Paul R., Reiser, Oliver
• Format: Article
• Language: English
• Subjects: heterogeneous catalysis; hybrid materials; magnetic nanoparticles; palladium complex; ROMPgel
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201000959

A novel hybrid material is reported as support for a recyclable palladium catalyst via surface immobilization of a ligand onto Co‐based magnetic nanoparticles (NPs). A standard “click” reaction is utilized to covalently attach a norbornene tag (Nb‐tag) to the surface of the carbon coated cobalt NPs. The hybrid magnetic nanoparticles are produced by initiating polymerization of a mixture containing both Nb‐tagged ligand (Nb‐tagged PPh3) and Nb‐tagged carbon coated cobalt NPs. In turn, the norbornene units are suitably functionalized to serve as ligands for metal catalysts. A composite material is thus obtained which furnishes a loading that is one order of magnitude higher than the value obtained previously for the synthesis of functionalized Co/C‐nanopowders. This allows for its application as a hybrid support with high local catalyst concentrations, as demonstrated for the immobilization of a highly active and recyclable palladium complex for Suzuki‐Miyaura cross‐coupling reactions. Due to the explicit magnetic moment of the cobalt‐NPs, the overall magnetization of this organic/inorganic framework is significantly higher than of polymer coated iron oxide nanoparticles with comparable metal content, hence, its rapid separation from the reaction mixture and recycling via an external magnetic field is not hampered by the functionalized polymer shell. Co/C‐nanomagnets are modified at the surface via immobilization of a norbornenyl‐tagged ligand using ROM polymerization to ultimately support palladium catalysts, which are applied in Suzuki‐Miyaura cross‐coupling reactions. The inherent advantage of such a hybrid material lies in the combined properties of the individual components, i.e., high catalyst loading invoked through the ROMP technology and magnetic fluidization/separation furnished by the highly magnetic nanobeads (158 emu g−1).