Various (aryloxo)(pentamethylcyclopentadienyl)titanium(IV) dichloride complexes of the type, Cp*TiCl2(OAr) [Cp* = C5Me5, Ar = 2,6-Me2C6H3 (1), 2,4,6-Me3C6H2 (2), 2,6-(Pr2C6H3)-Pr-i (3), 2,6-Pr-i(2)-4-'BuC6H2 (4), 2,6-'Bu2C6H3 (5), 2,6-'Bu-2-4-MeC6H2 (6)], have been prepared, and structures for 4 and 5 have been determined by X-ray crystallography. The Ti-O-C (phenyl) bond angles for the Cp* analogues containing the 2,6-diisopropyl-substituted phenoxo ligands (3-4, 173.0-174.6 degrees) were larger than those for other Cp* analogues (155.5-162.3 degrees), suggesting that both Cp* and 2,6-diisopropyl-substituted aryloxo ligand force the unique bond angle leading to more O -> Ti pi donation into Ti. Effect of aryloxide ligand in 1-hexene polymerization catalyzed by Cp*TiCl2(OAr)-MAO catalysts were explored, and 34 exhibited the exceptionally high catalytic activities. Various tert-BuCp analogues of the type, ('BuC5H4)TiCl2(OAr) [Ar = 2,6-Me2C6H3 (7), 2,4,6-Me3C6H2 (8), 2,6-(Pr2C6H3)-Pr-i (9), 2,6-Pr-i(2)-4-'BuC6H2 (10), 2,6-'Bu2C6H3 (11), 2,6-'Bu-2-4-MeC6H2 (12)], have also been prepared, and explored effect of the aryloxide ligand in syndiospecific styrene polymerization in the presence of MAO cocatalyst. The catalytic activity increased in the order: 10 (activity 2680 kg sPs/mol Ti h) > 7, 9 (1370) > 8 (534) > 11 (258) > 12 (54), strongly suggesting that role of anionic donor ligand was present in this catalysis. (c) 2006 Elsevier B.V. All rights reserved.