53.
Polymerization of propylene was conducted at 0 ∼ 150°C with the [ArN(CH
2)
3NAr]TiCl
2 (Ar = 2,6-
iPr
2C
6H
3) complex using a mixture of trialkylaluminium (AIR
3, R = methyl, ethyl and isobutyl) and Ph
3CB(C
6F
5)4 as cocatalyst. When AlMe
3 or AlEt
3 was employed, atactic polypropylene (PP) was selectively produced, whereas the use of Al(
iBu)
3 gave a mixture of atactic and isotactic PP. The isotactic index (I.I.; weight fraction of isotactic polymer) depended strongly upon the polymerization temperature, and the highest I.I. was obtained at ca. 40°C. The
13C NMR analysis of the isotactic polymer suggests that the isotactic polymerization proceeds by an enantiomorphic-site mechanism. It was also demonstrated that the present catalyst shows a very high regiospecificity.
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