Procedures have been developed at the Center for anchoring pre-formed homogeneous catalysts onto a variety of supports. These catalysts are designed to take advantage of the selectivity commonly found with homogeneous catalysts and the ease of separation and re-use associated with heterogeneous catalysts. In these Anchored Homogeneous Catalysts the catalytically active organometallic species is bound to the support through the metal atom of the complex so there is no need to modify the ligand present on the complex. Because of this factor, these species are particularly effective as heterogeneous enantioselective catalysts.
- These anchored catalysts have advantages over the use of the homogeneous catalysts.
- They are stable in multiple re-use with no deactivation.
- They do not deactivate when used at high substrate to catalyst ratios while some homogeneous catalysts may lose activity on prolonged exposure to hydrogen.
- They can be used in continuous reactors.
- They are at least as selective as the corresponding homogeneous catalyst.
- There is minimal metal loss in hydrogenations run using the anchored catalysts, usually less than 1 ppm of metal is found in the reaction mixtures.