Abstract: | (RCp)(R′Ind)ZrCl2 complexes 1 – 6 (Cp = cyclopentadienyl; Ind = indenyl; 1 , R = PhCH2 and R′ = H; 2 , R = PhCH2 and R′ = PhCH2; 3 , R = PhCH2CH2 and R′ = H; 4 , R = PhCH2CH2 and R′ = PhCH2; 5 , R = o‐Me? PhCH2CH2 and R′ = H; 6 , R = o‐Me? PhCH2 and R′ = H) were synthesized and characterized with 1H NMR, elemental analysis, mass spectrometry, and infrared spectroscopy. Their catalytic behaviors were compared with those of (Et3SiCp)(PhCH2CH2Cp)ZrCl2, (PhCH2Cp)2ZrCl2, (PhCH2‐ CH2Cp)2ZrCl2, (o‐Me? PhCH2CH2Cp)2ZrCl2, and (Ind)2ZrCl2 in ethylene polymerization in the presence of methylaluminoxane. Complex 5 showed high activity up to 2.43 × 106 g of polyethylene (PE)/mol of Zr h, and complex 4 produced PE with bimodal molecular weight distributions. The methyl group at the 2‐position of phenyl in complex 5 increased the activity greatly. The relationships between the polymerization results and the structures were analyzed with NMR spectral data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1261–1269, 2005 |