Homogeneous catalysts alternating copolymers

The scope of this chapter will be to focus on well-defined metal complexes that serve as homogeneous catalysts for the production of polycarbonates from epoxides and carbon dioxide. Although there are numerous such well-characterized metal complexes that catalyze this transformation, we will focus this chapter on recent contributions involving metal salicylaldimine (salen) and derivatives thereof [6, 7]. Some of the alternative catalysts systems are very active and selective for copolymer production. Most notably among these are the zinc p-diiminates reported by Coates and coworkers [8, 9]. These systems have been reviewed in detail elsewhere [10]. 

Palladium complexes figure prominently as well in the copolymerization of Q -olefins with carbon monoxide. Unlike the low molecular weight photodegradable random copolymers of ethylene and CO produced from a free-radical process, olefin/carbon monoxide copolymers produced from homogeneous palladium catalysts are perfectly alternating, the result of successive insertions of olefin and CO (Figure 19). Consecutive insertion of two similar monomers is either slow... 

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