Macromolecular metal complexes as catalysts with improved stability

Polymer-bound tertiary amine–copper complexes and polymer-bound phosphite–rhodium complexes were studied as catalysts for oxidative coupling of phenols and hydroformylation of alkenes, respectively. The activity and stability of these catalysts could be tuned or optimized by adapting the structure of the ligands and by changing the distance between adjacent ligands along the polymer chains. The latter effect has been described in terms of strain in the intermediate chain segments in the copper complexes or enhancement of the effective local ligand concentration around the rhodium complexes. So-called immobilized homogeneous catalysts were obtained by end-grafting of both types of macromolecular catalysts on to inert and insoluble silica particles. These immobilized polymeric catalysts could easily be separated and recovered. Under proper conditions a grafted polymerbound imidazole–copper complex and a new type of polymer-bound triphenyl–phosphite–rhodium complex showed excellent stability in continuous processes.