Propylene polymerization catalyzed by constrained geometry (cyclopentadienyl)phenoxytitanium catalysts

Abstract

Propylene polymerization was performed using three constrained geometry catalysts: 2-(tetramethylcyclopentadienyl)-4,6-di- tert-butylphenoxytitanium dichloride ( 1), 2-(tetramethylcyclopentadienyl)-6- tert-butylphenoxytitanium dichloride ( 2), and 2-(tetramethylcyclopentadienyl)-6-phenylphenoxytitanium dichloride ( 3) with Al( i Bu) 3/[Ph 3C] +[B(PhF 5)] 4 − as co-catalyst. The substituent effect of the ligand and the effect of the Al/Ti molar ratio on the catalytic properties were investigated. The catalytic activity decreases in the order of 1 > 2 > 3. The 13C NMR results show that the polymers are basically atactic polypropylene with some 2,1-insertion and 1,3-enchainment units in the polymer chain, and the end groups are mainly vinylidene (CH 2 CMe–) and vinyl (CH 2 CH–) together with a small amount of propenyl (CH 3CH CH–). A possible chain propagation and termination mechanism of the propylene polymerization was discussed.