67Isotactic polypropene was prepared using rac-dimethyl-silylbis(2-methyl-4-t-butyl-cyclopentadienyl)zirconiumdichloride (1) and methyla!umoxane (MAO) at temperatures between 0 and 80°C and with Al/Zr ratios of 300 and 1500. The polymers, prepared at temperatures below 30°C had melting points of 162°C and above. The chain ends were determined by means of distortionless enhancement by polarization transfer (DEPT)-NMR spectroscopy. The pentad intensities were corrected according to the chemical shifts of the end groups. The intensity distributions are shown to arise from enantiomorphic site control of the chiral catalyst species.