Trans-1,2-diphenylethylene bridged salicylaldiminato–isoindoline titanium(IV) chloride complexes: Synthesis, characterization and catalytic polymerization

The tridentate ligands, 4-R1-6-R2-2-{(trans-2-(isoindolin-2-yl)-1,2–diphenylethylimino) methyl}phenol (R1 = R2 = tert-butyl, 3a; R1 = Ph, R2 = H, 3b; R1 = R2 = H, 3c; R1 = R2 = Cl, 3d; R1 = R2 = Br, 3e; R1 = R2 = I, 3f) in which a substituted salicylaldiminato moiety and an isoindoline are linked by trans-1,2-diphenylethylene moiety have been prepared. Ligand 4-R1-6-R2-2-{(trans-2-(isoindolin-2-yl)-1,2–diphenylethylamino)methyl}phenol (R1 = R2 = tert-butyl, 4a; R1 = R2 = I, 4f) was obtained from the reduction of 3a and 3f with NaBH4 in methanol/THF solution at low temperature. Deprotonation of these tridentate ligands 3a–f, 4a and 4f by NaH at −78 °C in THF, followed by treating with 1.2 equiv of TiCl4 in toluene at room temperature, afforded the desired dark red titanium complexes[Ti(L)Cl3] (5a–f, 6a and 6f) in moderate to good yields. The structures of 5a and 6a were confirmed by single-crystal X-ray diffraction in the solid state. The metal atom has a distorted octahedral coordination geometry through the two nitrogen and one oxygen atoms from the tridentate ligand and three chlorides. These titanium complexes with such trans-1,2-diphenylethylene bridged tridentate ligands proved to be active to catalyze ethylene (co)polymerization with activity of 12.4–232.0 kg-polymer/mol(Ti)⋅h. The 13C NMR analysis of the polymer produced revealed that the polymer is highly linear polyethylene with no detectable branches and only very low amount of 1-hexene was incorporated into the main chain of the polyethylene.