Effects of substituents on cyclopentadienyl group for homopolymerization of ethylene, 1-hexene, and for ethylene/1-hexene copolymerization using a series of nonbridged (cyclopentadienyl)(ketimide)titanium complexes of the type, (CpTiCl2)-Ti-'(N=C'Bu-2) [Cp' = Cp (1),BuC5H4 (2), C5Me5 (Cp*, 3), and indenyl (4)] have been explored in the presence of methylaluminoxane (MAO) cocatalyst. Complexes 1-3 showed the similar catalytic activities for ethylene polymerization although the activity by 4 was somewhat low, whereas the activity for 1-hexene polymerization increased in the order 1 > 4 much greater than 2 > 3. These complexes showed significant activities for ethylene/1-hexene copolymerization affording high molecular weight poly(ethylene-co-1-hexene)s with unimodal molecular weight distributions, and the activity increased in the order: 4 > 1 much greater than 2, 3. The r(E)r(H) values in the polymerization by 1-3 at 40degreesC were 0.35-0.52 which clearly indicate that the 1-hexene incorporation in the copolymerization did not proceed in a random manner. The r(E) values by 1-3 were 6.0-6.4 and the values were independent upon the cyclopentadienyl fragment employed; the rE values by 4 at 40degreesC were 10.2-10.9 which were close to those by ansa-metallocene complex catalysts. These values were influenced by the polymerization temperature, and the 1-hexene incorporation by 1-4 became inefficient at higher temperature, although the observed activities especially by 1, 4 were highly remarkable. (C) 2004 Elsevier B.V. All rights reserved.