We investigated the catalytic performance of both bridged unsubstituted [rac-EtInd(2)ZrMe(2), rac-Me(2)Silnd(2)ZrMe(2)] and 2-substituted [rac-Et(2-MeInd)(2)ZrMe2), rac-Me2Si(2MeInd)(2)ZrMe2] dimethylbisindenylzirconocenes activated with triisobutyl aluminum (TIBA) as a single activator in (a) homo-polymerizations of ethylene and propylene, (b) copolymerization of ethylene with propylene and hexene-1, and (c) copolymerization of propylene with hexene-1 (at Al-TIBA/Zr = 100-300 mol/mol). Unsubstituted catalysts were inactive in homo-polymerizations of ethylene and propylene and copolymerization of propylene with hexene-1 but exhibited high activity in copolymerizations of ethylene with propylene and hexene-1. 2-Substituted zirconocenes activated with TIBA were active in homopolymerizations of ethylene and propylene and exhibited high activity in copolymerization of ethylene with propylene and hexene-1, and in copolymerization of propylene with hexene-1. Comparative microstructural analysis of ethylene-propylene copolymers prepared over rac-Me(2)Silnd(2)ZrMe(2) activated with TIBA or Me2NHPhB(C6F5)(4) has shown that the copolymers formed upon activation with TIBA are statistical in nature with some tendency to alternation, whereas those with borate activated system show a tendency to formation of comonomer blocks. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 29342941, 2010