The Covalent Attachment of Homogeneous Catalysts to Graphene Coated Cobalt Nanomagnets Enables a Rapid Catalyst Recovery

Many commercially important reactions including hydroformylation, hydrogenation and selective alcohol oxidation are conducted in the presence of homogeneous catalysts. The resulting problem of catalyst separation from the products is often very challenging and in some cases even non-economic. This leads to a high loss of valuable catalysts and precious noble metals.

The immobilization of homogeneous catalyst ligands using reliable C-C bond chemistry on magnetic nanoparticles offers a possible solution to this problem. The catalyst can then be easily removed from the reaction system by an external magnetic field. In the absence of the magnetic field however, the particles are small enough to rapidly diffuse and enable an efficient reactant conversion.

This contribution discusses the covalent functionalization of cobalt metal based nanomagnets and the subsequent derivatization to homogeneous catalyst ligands. A performance study using a technically important oxidation reaction confirms the advantageous use of a separable system without loss of activity.

References:

[1] R. N. Grass, E. K. Athanassiou, W. J. Stark, Angew. Chem. Int. Ed. 2007, 46, 4909.

[2] R. N. Grass, W. J. Stark, PCT Patent Application, Nov 2006.

[3] A. Schatz, R. N. Grass, W. J. Stark, O. Reiser, submitted 2008.

Figure 1 shows a transmission electron microscopy image of a carbon coated cobalt nanoparticle (left). The two photographs on the right display the rapid removal of the magnetic ligands by the use of a commercial neodymium magnet.