Synthesis, structure, and catalytic properties of ansa-zirconocenes, Me2X(Cp)(RInd)ZrCl2 (X=C, Si; R=2-p- or 3-p-tolyl)

Abstract

ansa-Zirconocenes Me2X(Cp)(3-TolInd)ZrCl2 [X = C(7), Si(8); Cp = eta(5)-C5H5; Tol = p-C6H4CH3] and Me2Si(Cp)(2-ToIInd)ZrCl2 (9), have been prepared by the reactions of ZrCl4 with the corresponding dilithiated ligands in diethyl ether at -78 degrees C. The molecular structure of complex 9 has been determined by a single crystal X-ray diffraction study. Propylene polymerization has been studied for complexes 7, 8 and 9 in the presence of methylaluminoxane (MAO). Complex 9 reveals the highest catalytic activity of 1570 kg PP/(mol Zr h atm) and the highest molecular weight of 1.2 X 10(6) among the three catalysts. Complex 9 produces atactic polypropylene (PP), whereas 7 and 8 afford PP with a weak syndiotacticity at low temperature.