Palladium(II)-Catalyzed Alternating Copolymerization and Terpolymerization of Carbon Monoxide with α-Olefins: Formation of Syndiotactic Copolymers as Well as Terpolymers with both Syndiotactic and Atactic Segments

[Pd(1,10-phenanthroline)(MeCN)₂](BF₄)₂ and related complexes were found to catalyze the alternating copolymerization of styrene derivatives with carbon monoxide to form syndiotactic copolymers with strictly head-to-tail arrangement in the polymer backbone. The polymers, as formed, were highly crystalline although the crystallinity (but not the stereoregularity) was lost upon dissolution in acids followed by reprecipitation. The Pd(II) catalysts were also found to catalyze the terpolymerization of ethylene, propylene, ω-undecylenyl alcohol, and ω-methyl undecylenate with styrene and carbon monoxide. At high ratios of styrene to the second olefin, the terpolymers formed had structures consisting of syndiotactic alternating styrene-CO blocks randomly separated by atactic spacers formed by the alternating second olefin-CO units. The tactic styrene-CO blocks were lost with increasing content of the second olefin.