Vanadium(V) Complexes Containing Tetradentate Amine Trihydroxy Ligands as Catalysts for Copolymerization of Cyclic Olefins

A series of vanadium(V) complexes bearing tetradentate amine trihydroxy ligands [NOOO], which differ in the steric and electronic properties, have been synthesized and characterized. Single crystal X-ray analysis showed that these complexes are five or six coordinated around the vanadium center in the solid state. Their coordination geometries are octahedral or trigonal bipyramidal. In the presence of Et2AlCl, these complexes have been investigated as the efficient catalysts for ethylene polymerization and ethylene/norbornene copolymerization at elevated reaction temperature and produced the polymers with unimodal molecular weight distributions (MWDs), indicating the single site behaviors of these catalysts. Both the steric hindrance and electronic effect of the groups on the tetradentate ligands directly influenced catalytic activity and the molecular weights of the resultant (co)polymers. Other reaction parameters that influenced the polymerization behavior, such as reaction temperature, ethylene pressure, and comonomer concentration, are also examined in detail. Furthermore, high catalytic activities of up to 3.30 kg polymer/mmol(v).h were also observed when these complexes were applied to catalyze the copolymerization of ethylene and 5-norbornene-2-methanol, producing the high-molecular-weight copolymers (M-w = 157-400 kg/mol) with unimodal MWDs (M-w/M-n = 2.5-3.0) and high polar comonomer incorporations (up to 12.3 mol %). (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1122-1132, 2010