Catalysts using organometallic polymers

Pincer compounds with a general structure like 20 are common in organo-metallic chemistry [832]. They are useful as precursors to catalysts and as components of hybrid organometallic polymers [84-86]. In most cases, they have high stability to oxygen and water in addition to high thermal stability. 

Each process results in a different type of polymer (10,13). A wide variety of organometallic catalysts useful for polymerization has been described (14). 

Slcreospecific solution polymerization has been emphasized since the discovery of the complex coordination catalyses that yield polymers or butadiene and isoprene having highly ordered microstructures. The catalysts used are usually mixtures of organometallic and transition metal compounds. An example of one of these polymers is cis- 1.4-polybutadiene. 

Dimethylketene was subjected to polymerisations catalysed with various organometallic compounds. It was found to form highly crystalline polymers, the structure of which depended on the kind of organometallic catalyst used. 

Mo and W catalysts used by other researchers for the polymerization of acetylenes are shown in Table 7. They are all organometallics, and are usually less active than those in Table 3. It is reported that ladder polymers form from acetylenes in the presence of the toluene Mo(CO)3 complex 8). Katz and Lee have succeeded in polymerizing acetylenes with Fischer s carbene (3 a) and Casey s carbene (3b)9) ... 

Surface functionalization with polymer and block-co-polymer films using organometallic catalysts has been... 

The first example of asymmetric organometallic catalysis outside the area of polymer chemistry was the cyclopropanation of alkenes as described by Nozaki, Noyori et al. in 1966 [17]. The chiral catalyst used was a salen-copper complex 3 (Scheme 3), giving a maximum enantioselectivity of 10% ee. These low but well-established values initiated further research in this area. Later, Aratani et al. initiated the tuning of the structure of the copper catalyst at Sumitomo [18]. They were able to reach quite high level of enantioselectivity with copper catalyst 4. For example, 2,2-dimethyl-cyclopropane carboxylic acid was obtained in 92% ee, and subsequently used in a process to prepare cilastatine. 

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