Significant Polar Comonomer Enchainment in Zirconium-Catalyzed, Masking Reagent-Free, Ethylene Copolymerizations

In principal, the direct copolymerization of ethylene with polar comonomers should be the most efficient means to introduce functional groups into conventional polyolefins but remains a formidable challenge. Despite the tremendous advances in group 4-centered catalysis for olefin polymerization, successful examples of ethylene + polar monomer copolymerization are rare, especially without Lewis acidic masking reagents. Here we report that certain group 4 catalysts are very effective for ethylene + CH₂=CH(CH₂)_nNR₂ copolymerizations with activities up to 3400 Kg copolymer mol⁻¹-Zr h^-1 atm^-1, and with comonomer enchainment up to 5.5 mol % in the absence of masking reagents. Group 4 catalyst-amino-olefin structure–activity-selectivity relationships reflect the preference of olefin activation over free amine coordination, which is supported by mechanistic experiments and DFT analysis. These results illuminate poorly understood facets of d⁰ metal-catalyzed polar olefin monomer copolymerization processes.