Olefin polymerization behavior of bis(phenoxy-imine) Zr, Ti, and V complexes with MgCl2-based cocatalysts

Abstract

This contribution reports on the olefin polymerization behavior of phenoxy-imine ligated Zr, Ti, and V complexes 1–10 with MgCl2/RmAl(OR)n systems. Zr complexes 1–4 combined with MgCl2/RmAl(OR)n display strikingly high ethylene polymerization activities; indeed, they are some of the highest reported activities for methylalumoxane (MAO)- and borate-free olefin polymerization catalysts (max. 1819 kg-PE/(mmol-cat h), 0.9 MPa ethylene pressure, 50 °C). In addition, when Ti complexes 5–7 are combined with MgCl2/RmAl(OR)n they exhibit high ethylene polymerization activities (max. 36.3 kg-PE/(mmol-cat h), 0.9 MPa ethylene pressure, 50 °C) and produce polyethylenes with narrow molecular weight distributions (Mw/Mn) and ethylene–propylene copolymers with homogeneous structures, representing the first examples of MAO- and borate-free, highly active single-site catalyst systems. The activities exhibited by the Zr and Ti complexes with MgCl2/RmAl(OR)n are superior or comparable to those obtained with MAO cocatalyst systems. Moreover, V complexes 9 and 10 in association with MgCl2/RmAl(OR)n demonstrate high activities at elevated temperatures (9: 75 °C, 65.1 kg-PE/(mmol-cat h), atmospheric ethylene pressure) and are the first reported examples of highly active, thermally robust single-site V-based olefin polymerization catalysts. All of the polyethylenes formed from the MgCl2/RmAl(OR)n systems display good polymer morphology, indicating that complexes 1–10 are heterogenized on the surface of the MgCl2/RmAl(OR)n. These results suggest that MgCl2/RmAl(OR)n not only works as an excellent cocatalyst, but is also a good support for phenoxy-imine ligated Zr, Ti, and V complexes.