Polymerization of carboxylic ester functionalized norbornenes catalyzed by (η3‐allyl)palladium complexes bearing N‐heterocyclic carbene ligands

Abstract

AbstractAn in situ generated cationic allylpalladium complex bearing N‐heterocyclic carbene (NHC) ligands, derived from the reaction of [(η3‐C3H5)Pd(NHC)Cl] with AgX (X = BF4 or SbF6), is an active catalyst for the addition polymerization of norbornene and norbornene derivatives [5‐norbornene‐2‐carboxylic acid methyl ester (b) and 5‐norbornene‐2‐carboxylic acid n‐butyl ester (c)] with an ester group containing a large portion of endo‐isomers. The catalytic activities, polymer yields, molecular weights, and molecular weight distributions of polynorbornenes were investigated under various reaction conditions: the catalytic activity was highly dependent on the counteranion, the reaction solvent, and the reaction temperature. For b, as the portion of an endo‐isomer increased, the activity of 13(SbF) was much higher than those of 14 and 15, and for c (exo/endo = 95:5), the maximum turn over number (TON) was observed with 15(SbF). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3042–3052, 2007