Facile Syntheses of Bis[1-(arylimino)ethyl]pyridine−MoCl₃/MMAO Catalytic Systems and Their Dual Catalytic Functions for ROMP of Norbornene and Linear Polymerization of Ethylene

ROMP (ring-opening metathesis polymerization) of norbornene using a series of 2,6-bis[1-(arylimino)ethyl]pyridine−MoCl₃/cocatalyst systems was explored, and the 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine−MoCl₃ (5)/MMAO (modified methylaluminoxane, AlMeO:Al-isoBuO = 3:1) system particularly exhibits a high catalytic activity at 60 °C for norbornene polymerization leading to high molecular weight polymers with high cis contents (98−100%). The 2,6-bis[1-(arylimino)ethyl]pyridine−MoCl₃/AlEt₃ systems catalyzed the norbornene polymerization in high yields, but the cis selectivities were rather low. The 5/MMAO system is also effective for the polymerization of endo-dicyclopentadiene at 60 °C, leading to soluble polymers with 100% cis content, and for the polymerization of ethylene with high activity (44.5 × 10³ g of PE/(mol h)) to lead to linear polymers (M_n = 16.8 × 10⁴). Attempts to prepare ethylene−norbornene block copolymers failed, and a mixture of homopoly(norbornene) and homopoly(ethylene) was obtained.