Alternating Copolymers from Alkenes and Carbon Monoxide

Alternating Copolymers from Alkenes and Carbon Monoxide 

Eite Drent, Johannes A. M. van Broekhoven, and Peter H. M. Budzelaar 

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], 

The discovery of efficient catalysts for the copolymerization of alkenes originated from a study of the alkoxycarbonylation of ethylene in methanol (MeOH) to methyl propionate [Eq. (1)]. 

The catalysts were cationic palladium-phosphine systems prepared from palladium acetate, an excess of triphenylphosphine (PPh3), and a Bronsted acid of a weakly or noncoordinating anion (e.g., p-tosylate (OTs ) methanol was used as both the solvent and a reactant. An unexpected change in selectivity was observed upon replacement of the excess of PPh3 by a stoichiometric amount of the hidentate l,3-bis(diphenylphosphino)propane (dppp). Under the same conditions, these modified catalysts led to perfectly alternating ethylene/CO copolymers with essentially 100% selectivity [Eq. (2)] [12-14]. 

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