We have developed procedures for anchoring pre-formed homogeneous catalysts onto a variety of supports using heteropoly acids (HPA) as the anchoring agents. [Chem. Commun., 1257 (1999); US Patent # 6,025,295 (2000)] These catalysts are designed to take advantage of the selectivity commonly found with homogeneous catalysts and the ease of separation and reuse associated with heterogeneous catalysts. They have been found to be at least as active and selective, if not more so, than the homogeneous analogs and have been reused many times with no loss of activity or selectivity. Some of these anchored catalysts have been re-used ten to fifteen times with no loss of activity of selectivity. Catalyst leaching was not observed. Since the homogeneous catalyst is bound to the support through the metal atom of the complex, there is no need to modify the ligand present on the complex. Because of this factor, these anchored species are particularly effective as heterogeneous enantioselective catalysts. This type of bonding was based on the published structures of the complexes formed by the interaction of Rh(COD) with a Keggin HPA (Finke, et al., Inorg. Chem., 34, 1413 (1995).

This technique has been successfully used to prepare a number of different anchored homogeneous catalysts from both rhodium and ruthenium complexes. Materials such as alumina, carbon, silica, lanthana and clay have all been used as supports. The HPA's, phosphotungstic acid (PTA), silicotungstic acid (STA), phosphomolybdic acid (PMA) and silicomolybdic acid (SMA) have all been used as anchoring agents with varying degrees of success. Most of our work, to date, has used PTA as the anchoring agent and the data we have on the other HPA's indicate that this is probably the one to use for most reactions. Pre-hydrogenation of the catalyst before introduction of the substrate improved catalyst activity and selectivity.

The low pressure reactors described in Our Facilities are the best to use with the anchored homogeneous catalysts selectivity in the desired reaction.

With these catalysts our approach is to work closely with the client in developing the appropriate procedure for catalyst preparation and possible treatment as well as the reaction conditions required for optimum selectivity in the desired reaction. Johnson Matthey, Inc. is marketing these catalysts.