When polymerization of propene was conducted using the C-2-symmetrical zirconocenes racEt(2,4,7-Me(3)Ind)(2)ZrCl2 (I) and rac-Me2Si(2-Me-4-Ph-Ind)(2)ZrCl2 (II) combined with Ph(3)CB(C6F5)(4), the isotacticity ([mmmm]) and the melting point (T-m) of the produced polymer markedly increased, along with a decrease of the polymerization temperature from 30 to -78 degrees C. Thus, isotactic polypropene (iPP) with T-m = 168.9 degrees C was obtained from the polymerization with catalyst I at -78 degrees C, whereas the [mmmm] and T-m of iPP were almost unchanged in the same temperature range when the C-1-symmetrical zirconocene iPr(3-tBuCp)(3-tBuInd)ZrCl2 (III or III’) was employed.