Synthesis and structural analysis of various phenoxy modified half-titanocenes with different anionic ligands of the type, Cp*TiX(Y)(O-2,6-(Pr2C6H3)-Pr-i) [X = Y = pyr (2, pyr = C4H4N), pz (3, C3H3N2), OPh (4); X =Cl, Y = OCH(CF3)(2) (5)] have been explored. Ethylene/styrene copolymerization by 2, 5, and Cp*TiCl2(O-2,6-(Pr2C6H3)-Pr-i)(1) in the presence of [PhN(H)Me-2][B(C6F5)(4)] and Al(i-Bu)(3)/Al(n-octyl)(3) afforded poly(ethyleneco-styrene)s as the sole product even at 55 and 70 degrees C, whereas the pyrazolato analogue (3) showed the negligible activity and 4 afforded a mixture of copolymer and syndiotactic polystyrene: 5 showed the better catalyst performance in terms of activity, suggesting that the anionic ligand (X,Y) plays a role in this catalysis. (C) 2012 Elsevier B.V. All rights reserved.