The effects of different electron donors such as ethyl benzoate(EB) diisobutyl phthalate (DIBP)

2

2

6

6-tetramethyl piperidine(TMP) and various silanes as internal donor (Din) and external donor(Dex) respectively were investigated.The possible synergistic effect of Din and Dex was discussed.It was found that EB

DIBP

TMP and alkoxysilanes used as Dex could evidently improve the stereospecificity accompanied with a decrease of the activity

while the effects of EB

DIBP and TEM used as Din are quite differet from each other. The effects of increasing the stereospecilicity is due to deactivation of different selectivity for both atactic and isotatic active centers and the deactivation of atacitic active centers is much greater than that of isotactic active centers. Cooperation of appropriate Din and Dex would give good catalytic performance with high activity andhigh stereospectifity.