Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

Abstract

A series of group 4 metallocenes (RCp)[Cp―(bridge)―(2‐C4H3S)]MCl2 [M = Ti (C1, C2, C3, C4); M = Zr (C5, C6, C7, C8)] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single‐crystal X‐ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1, C2, C3, C4 showed moderate catalytic activities and produced high‐ or ultra‐high‐molecular‐weight polyethylene (Mv 70.5–227.1 × 104 g mol−1). Titanocene C3 is more active and long‐lived, with a lifetime of nearly 9 h at 30 °C. At elevated temperatures of 80–110 °C, zirconocenes C5, C6, C7, C8 displayed high catalytic activities (up to 27.6 × 105 g PE (mol Zr)−1 h−1), giving high‐molecular‐weight polyethylene (Mv 11.2–53.7 × 104 g mol−1). Even at 80 °C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system. Copyright © 2014 John Wiley & Sons, Ltd.