Cocatalyst Effect in Transition Metal Catalyzed Ethylene Polymerization and Copolymerization

Abstract Transition‐metal‐based olefin polymerization catalysts usually require activation with a cocatalyst to initiate polymerization reactions. Borane type cocatalyst is one of the most important classes of cocatalysts that can significantly influence the catalytic performances. In this contribution, we designed and prepared a series of borane cocatalysts, and subsequently investigated their properties in a titanium‐based Constrained Geometry Catalyst ( CGC‐Ti ) catalyzed ethylene polymerization and ethylene/1‐octene copolymerization. Among these borane cocatalysts, B(C 6 F 5 ) 2 OtBu exhibited outstanding cocatalyst performances, achieving activity of up to 1.06×10 7 g mol −1 h −1 and polymer molecular weight of up to 88.2×10 4 g mol −1 in ethylene polymerization. In ethylene/1‐octene copolymerization, this borane enabled activity of up to 2.46×10 6 g mol −1 h −1 , affording copolymers with comonomer incorporation of up to 12.8 % and copolymer molecular weight up to 18.3×10 4 g mol −1 . The superior properties of B(C 6 F 5 ) 2 OtBu originated from its unique activation mode with the oxygen atom being coordinated to the active metal center.