Preparation of Supported Complex Catalysts

A number of materials have been used as the basic support (Table I). Although it is convenient to describe them as either inorganic or organic supports, there is, as with most classification schemes, a considerable 

Metal oxides such as alumina Polyallyls Polybutadiene Polyamino acids Urethanes Acrylic polymers Cellulose Cross-linked dextrans Agarose 

Several research groups have concentrated on attaching metal complexes to silica by introducing phosphine groups on to the surface. They have used two approaches that differ only in the order of the steps (2, 4, 5, 87)  

The main disadvantage of reaction (3) is the difficulty of determining the precise nature of the catalytic site since this is formed in the support. Reaction (4) was designed to obviate this problem since, in principle, the complex is isolated and may be characterized by standard methods. In practice, however, many complexes of this type cannot be isolated as crystalline solids but only as oils that must be purified chromatographi-cally using nonhydroxylic phases. 

Although reactions (1)—(4) are the only reactions that appear to have been used in preparing supported metal catalysts, there are several other ways that could be used, for example, 

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