Copolymerization olefin-carbon monoxide

The copolymerization of carbon monoxide and a-olefins is one of the most challenging problems in polymer synthesis. Sen and his coworkers discovered that some cationic palladium compounds catalyze this alternative copolymerization, giving polyketones (Eq. 13). 

In addition to a-olefins, p-/-butylstyrene can be used as a comonomer for the isotactic specific copolymerization with carbon monoxide with chiral induction [32], Whereas bipyridyl as ligand gives a syndiotactic polymer, the Pd-catalyzed polymerization with ligand 11 leads to a polymer with isotacticity of over 98% and high optical activity ([ ]D -536° (in CH2C12)) [33, 34]. The BINAPHOS catalyst described above is also effective in this type of copolymerization [25],... 

Drent, E., van Broekhoven, J. A. M., Doyle, M. J. and Wong, P. K., Palladium Catalyzed Copolymerization of Carbon Monoxide with Olefins to Alternating Polyketones and Polyspiroketals , in Ziegler Catalysts, Springer-Verlag, Berlin, 1995, pp. 481 196. 

Semiyen, J. A. Ring-Chain Equilibria and the Conformations of Polymer Chains. Vol. 21, pp. 41-75. Sen, A. The Copolymerization of Carbon Monoxide with Olefins. Vol. Tip4, pp. 125-144. 

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... 

This is the case, for example, in the copolymerization of carbon monoxide and ethylene where the CO will not add to itself but does copolymerize with the olefin monomer. General theoretical treatments have been developed for such cases, taking into account temperature and penultimate effects. Again, the superiority of these more complicated theories over the simpler copolymer model is not proved for all systems to which they have been applied. 

The copolymerization of alkenes with carbon monoxide has attracted the attention of chemists for many years [1]. Following the commerciahzation of Carilon, an alternating olefin carbon monoxide terpolymer based on ethene and small amounts (5-10%) of propene (Scheme 8.1, 1), by Shell [2, 3] in the 1990s interest in the identification of new and more active catalysts and of the stereochemical characteristics of the reaction has grown. 

When l-olefins are used as the substrate for the copolymerization with carbon monoxide, different moieties can form due to the absence of symmetry elements relating to the two unsaturated carbon atoms and to the enantiofaces of the olefin substrate (four different insertion pathways) (Scheme 8.11) [29]. 

The copolymerization of ethylene and carbon monoxide to give alternating copolymers has attracted considerable interest in both academia and industry over recent decades [1, 2]. Attention was focused on aliphatic polyketones such as poly(3-oxotrimethylene) (1) because of the low cost and plentiful availability of the simple monomers. The new family of thermoplastic, perfectly alternating olefin/ carbon monoxide polymers commercialized by Shell provides a superior balance of performance properties not found in other commercial materials the an ethylene/ propene/CO terpolymer is marketed by Shell imder the tradename Carilon . About the history of polyketones see Refs. [3-11],... 

Ethylene and other olefins can also be copolymerized with carbon monoxide to form polymers of aliphatic ketones, using transition metal catalysts, like paUadium(ll) coupled with non-coordinating anions. There are numerous reports of such catalysts in the literature. One example is a compound composed of bidentate diarylphosphinopropane ligand and two acetonitrile molecules coordinating Pd coupled with BF3 counterions. This compound, bis(acetonitrile)palladium(II)-l,3-bis(diphenyl-phosphino)propane-(tetrafluoborate), can be illustrated as follows [97] ... 

The first palladium-catalyzed copolymerization of carbon monoxide (CO) with olefins was described in 1982 [11], and as a consequence, carbonylative coupling reactions with alkenes were reported soon after. Notably, it was Negishi and Miller who discovered the first two examples of intramolecular carbonylative Heck reactions of 1-iodopenta-1,4-dienes by applying stoichiometric amounts of palladium [12]. 5-Methylenecyclopent-2-enones as the products were produced in moderate yields (Scheme 7.1). 

The copolymerization of carbon monoxide and olefins forms the polyketone in Equation 17.65, and this polymerization is closely related to the hydroesterification and hydrocarboxylation of olefins. The rate of reaction of the acyl intermediate that was generated in the hydroesterification process with olefin or alcohol differentiates the formation of copolymer from the formation of monomeric esters. This difference in relative rates for reaction of the acyl intermediate with olefin versus alcohol results from a change in the ancillary ligand on the palladium, as described in this section. 

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