(177a) Ossification: A New Approach for Immobilization of Homogeneous Catalysts

The immobilization of soluble metal complex catalysts has gained considerable attention in the last 2-3 decades due to the difficulties in separating the soluble catalysts from products. Various concepts have been explored and applied to a variety of reactions. The recent trends in homogeneous catalysis with discoveries of new synthetic routes in fine and specialty products (including optically active pharmaceuticals) further demand efficient approaches for catalyst-product separations, wherein the immobilization has particular significance. A common problem has been the leaching of expensive metals from the immobilized catalysts and the relatively lower catalytic activities observed. Thus, the design and development of novel methodologies for immobilization to finally achieve highly active, selective and stable catalysts remains a challenging task.

In this presentation, a new approach of immobilization-?Ossification? would be described which has been shown to be highly promising to synthesize active, selective and stable catalysts for carbonylation and hydroformylation reactions. The ?ossification? involves synthesis of inherently insoluble catalytically active metal complex from its soluble analogues by a systematic molecular modification, which resembles with self assembly of naturally occurring biomaterials (e.g. shells, bones and coral reefs). This allows synthesis of novel immobilized catalysts which are insoluble in most organic and aqueous media. The ?ossification? is a generic approach and applicable to a variety of catalytic reactions. In this presentation, examples of carbonylation and hydroformylation reactions using ossified Pd and Rh complex catalysts will be discussed including the comparison with homogeneous and immobilized catalysts prepared by other known methods.