Synthesis of phenoxy-ester titanium complexes with different R₁ and R₂ substituents and their catalytic properties

A series of phenoxy-ester ligated titanium complexes with different R₁ and R₂ substituents was synthesized. The structures of 3-silylsubstituted salicylate ligands and their corresponding titanium complexes were characterized using infrared spectrometer, nuclear magnetic resonance spectroscopy and mass spectrometer. The novel [O, O] bidentate coordination compounds with different R₁ and R₂ substituents were then used as the catalysts for ethylene-propylene copolymerization together with ⁱBu₃A1/Ph₃CB(C₆F₅)₄ as the cocatalysts in toluene. The correlations between R₁, R₂ substituents of titanium complexes and polymerization activity, polymer molecular weight were studied. The catalytic activity of titanium complex was observed to decline with increasing the size of R₂, whereas the copolymers with higher molecular weight were synthesized using the titanium complex with larger R₁ substituent. The ethylene propylene copolymers prepared using different titanium complex catalysts were all random copolymers.