The homogeneous homopolymerization of propene was conducted with the two catalyst precursors Me2Si(Ind)(2)ZrBz(2) (I) and Me2Si(2-Me-4-Ph-Ind)(2)ZrBz(2) (2) and triphenylmethyltetrakis(pentafluorophenyl)borate [C(CH3)(3)][B(C6F5)(4)] (3) as cocatalyst. After synthesizing the dibenzyl compounds from their dichloride derivatives the catalyst system (1)/(3) was optimized in respect to the catalyst/cocatalyst ratio and the amount of tri(isobutyl) aluminum (TIBA). The polymerization behavior of the catalyst system (2)/(3) is investigated using a central composite experimental design. In this design the dependence of the polymer properties on temperature, catalyst and monomer concentration are modeled. The dibenzyl compound (2) shows extremely high catalytic activities of 600 000 kg PP/mol(Zr) h mol(p). The polymers produced with this catalyst exhibit very high melting points and molecular weights. (C) 2001 Elsevier Science Ltd. All rights reserved.