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

Treatment of MCl3(OC6H3-2-tBu-6-CH==NC6F5)(THF) (M = Ti, Zr) with a variety of different potassium iminopyrrolate salts (K+[RN==CHC4H3N]-), (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-CH==NC6F5)(C2H5N==CHC4H3N) (1c), TiCl2(OC6H3-2-tBu-6-CH==NC6F5)(C6H11N==CHC4H3N) (1b) and ZrCl2(OC6H3-2-tBu-6-CH==NC6F5)(C6H11N==CHC4H3N) (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.