Electronic Effects in Monoindenyl‐Ketimide Titanium Catalysts for Ethylene (Co)polymerization

A series of half‐titanocene catalysts containing ketimine ligands have been successfully designed and synthesized, with the general formula IndTiYCl 2 (where Ind = indenyl). The effects of substituents with different electronic properties on ethylene homopolymerization, ethylene/1‐octene copolymerization and ethylene/norbornene (NB) copolymerization are investigated. In ethylene homopolymerization, the order of catalytic activity is Ti3 [NC( t Bu)(4‐NMe 2 Ph)] > Ti2 [YNC ( t Bu)(4‐ t BuPh)] > Ti4 [YNC t BuPh] > Ti1 [YNC ( t Bu)(4‐FPh)], which indicates that electron donating substituents are crucial to promote the reaction. Moreover, the electron donor substituent can also enhance the catalytic performance of ethylene/1‐octene copolymerization. In the copolymerization of ethylene and norbornene, the polymers produced by these catalytic systems showed remarkable catalytic activity, high molecular weight and norbornene insertion rate. In contrast, the catalysts with electron withdrawing substituents performed better in ethylene/norbornene copolymerization.