Stereoselective alternating copolymerization of carbon monoxide with olefins

Completely alternating copolymerization of carbon monoxide with alpha-olefins proceeds in a highly enantioselective manner using chiral Pd( II) complexes. Here we review the recent development in this area. The completely alternating feature of this capolymerization has been studied by kinetics and theoretical calculations. In order to central the regio- and enantioselectivity of olefin insertion, three kinds of chiral bidentate ligands have been reported: bis(dialkylarylphosphine), bisoxazoline, and phosphine-phosphite. The last one is applicable to the reaction of a wide range of alpha-olefins, such as aliphatic 1-alkenes and styrene derivatives, affording completely alternating copolymers with almost complete head-to-tail regioselectivity, isotacticity, and enantioselectivity. alpha,omega-Dienes and allenes also give alternating copolymers. Characteristic features of the chiral phosphine-phosphite-Pd (II) system are discussed in relation to the reaction mechanism and the enantiofacial-descriminating step.