Novel bidentate phosphine modified Pd(acac)2/BF3OEt2 catalyst system for the homopolymerization of alkylnorbornenes and copolymerization with norbornene

The Pd(acac)2+nPh2P(CH2)mPPh2+25BF3OEt2, n=1-3, m=1-6, catalyst system has been successfully employed for the homopolymerization of 5-alkyl-2-norbornenes and their copolymerization with norbornene. For this series, the most efficient catalyst system was Pd(acac)2+2Ph2P(CH2)4PPh2+25BF3OEt2. The activity of the catalyst system is comparable to that of most active late transition metal catalysts described in the literature. Bidentate phosphines containing bridges larger than 1,4-butane are likely to act as monodentate ligands. The incorporations of flexible alkyl groups onto the main chain of norbornene, as well as copolymerization of 5-alkyl-2-norbornenes with norbornene, represent a useful method for lowering the glass transition temperature (Tg), i.e. improving the processability. The introduction of bidentate phosphine ligand to the Pd(acac)2+25BF3OEt2 system switched the carbocationic polymerization mechanism to the coordination Ziegler-Natta polymerization. The simplicity of this catalytic system composition might be of industrial importance.