Substrate selectivity by the polymer support in hydrogenation over crosslinked polymer-immobilized metal catalysts

Metal clusters were immobilized on crosslinked polymers by two methods. One is the immobilization of polymer-protected platinum or rhodium clusters by covalent bond formation between the protective polymer and the crosslinked polymer support. The immobilization was attributed to the formation of amide bonds by the reaction of methyl acrylate residues of the protective polymer with amino groups of the aminoethylated polyacrylamide gel. In the other method, palladium clusters were immobilized on chelate resin-metal complexes by reduction of palladium ions supported on the resin complexes which are characterised by high porosity. In this case the chelate resin works as both the support and as the protective polymer of the clusters. Both the immobilized metal clusters preferably catalyzed the hydrogenation of C=C bonds in hydrophilic substrates, in particular the substrate containing a carboxyl group. This substrate selectivity can be explained by the acid-base interaction between the substrate and the polymer support.