Mixed-ligand iminopyrrolato-salicylaldiminato group 4 metal complexes: Optimising catalyst structure for ethylene/propylene copolymerisations

Treatment of MCl₃(OC₆H₃-2-^tBu-6-CHNC₆F₅)(THF) (M = Ti, Zr) with a variety of different potassium iminopyrrolate salts (K⁺RNCHC₄H₃N]⁻), (R = phenyl, cyclo-hexyl, ethyl) afforded the corresponding titanium and zirconium mixed-ligand complexes MCl₂(N-O)(N-N). The molecular structures of TiCl₂(OC₆H₃-2-^tBu-6-CHNC₆F₅)(C₂H₅NCHC₄H₃N) (1c), TiCl₂(OC₆H₃-2-^tBu-6-CHNC₆F₅)(C₆H₁₁NCHC₄H₃N) (1b) and ZrCl₂(OC₆H₃-2-^tBu-6-CHNC₆F₅)(C₆H₁₁NCHC₄H₃N) (2b) show distorted octahedral geometries with trans-O⁻,N⁻/cis-Cl₂ arrangements. On activation with MAO the titanium (iminopyrrolato)(salicylaldiminato) complexes show excellent activities in ethylene polymerisation and are significantly more effective ethylene/propylene copolymerisation catalysts, both in terms of activity and propene incorporation, than either of the parent complexes. The ethylene-propylene copolymers show ca. 80% 1,2 regioselectivity and at high propylene incorporation tend towards an alternating structure.