(Trialkylsilyl-cyclopentadienyl)titanium(iv) dichloride complexes containing ketimide ligands, Cp′TiCl2(NCtBu2) (Cp′ = Me3SiC5H4, Et3SiC5H4), as efficient catalysts for ethylene copolymerisation with norbornene and tetracyclododecene†

Trialkylsilyl-substituted half sandwich titanium complexes containing ketimide ligands, (RC₅H₄)TiCl₂(NC^tBu₂) (R = SiMe₃, SiEt₃), especially the SiEt₃ analogue, exhibited superior catalytic activities with efficient norbornene (NBE) incorporation (25 700–91 400 kg polymer per mol Ti h⁻¹; NBE 36.2–72.7 mol%) in the ethylene/NBE copolymerisation at 50 °C to afford high molecular weight copolymers with high NBE contents (NBE > 60 mol%). These complexes also displayed superior capability for efficient synthesis of ethylene copolymers with tetracyclododecene (TCD) at 50 °C, and synthesis of high molar mass copolymers with high glass transition temperatures (T_g = 255 °C, TCD 52.3 mol%) has been achieved. Efficient synthesis of high molar mass cyclic olefin copolymers (COCs) possessing high T_g values has been demonstrated by using these catalysts.