Half-titanocene complexes bearing bulky dibenzhydryl-substituted aryloxide ligand: Syntheses, characterization, and ethylene (Co-)polymerization behaviors

Three half-titanocene complexes 2a-3a bearing dibenzhydryl-substituted aryloxide ligands CpTiCl₂(O-2,6-Ph₂[Formula presented]₆H₂-4-Me), 2a; CpTiCl₂ (O-2,6-Ph₂[Formula presented]₆H₂-4-OMe), 2b; Cp*TiCl₂(O-2,6-Ph₂[Formula presented]₆H₂-4-Me), 3a were synthesized. All the complexes were characterized by NMR spectroscopy and elemental analysis. The molecular structures of complex 2a and 2b were further determined by single crystal X-ray diffraction, both of them adopt a three-legged distorted tetrahedral geometry in which the aryl substituents are orthogonally to the aryloxide group. Activated by methylaluminoxane (MAO), these complexes showed high activities (up to 2100 kg mol⁻¹ (Ti) h⁻¹) for ethylene polymerization. The resultant polyethylenes had high molecular weight and narrow molecular weight distributions. Furthermore, for the ethylene/1-hexene copolymerization, these complexes exhibited moderate activites and moderate to high 1-hexene incorporation ability. The sequence distributions of poly (ethylene-co-1-hexene)s are greatly influenced by the substituent on the cyclopentadineyl group of titanium complexes.