Polymerization of 5-norbornene-2-methyl acetate catalyzed by air-stable cationic (η3-substituted allyl) palladium complexes of N-heterocyclic carbene

In situ generated cationic (η3-substituted allyl) palladium N-heterocyclic carbene (NHC) complexes are air-stable active catalysts for the olefin polymerization of (bicyclo[2.2.1]hept-5-en-2-yl)methyl acetate (5-norbornene-2-methyl acetate) (endo:exo = 7:3). Catalytic activities, polymer yields, molecular weights, and molecular weight distributions of polymers were investigated under various reaction conditions. The catalytic activity was highly dependent not only on the reaction condition such as a solvent or the reaction temperature but also on the structure of the catalyst that include substituents of the allyl group in the catalyst and the counter anion. As the bulkiness of the allyl group increased, the catalytic activity of the catalysts increased.

Graphical abstractIn situ generated air-stable cationic allyl palladium N-heterocyclic carbene (NHC) complexes were used as catalysts for vinyl-addition polymerization of 5-norbornene-2-methyl acetate. As the steric bulkiness of the substituent(s) on the allyl group increases, the catalyst became more stable and the catalytic activity of the catalyst increased.Figure optionsDownload full-size imageDownload as PowerPoint slide