Four monomeric titanium(IV) dichloride complexes of amine-bis(phenolate) ligands having an extra donor arm (2a-2d) and one oxo-bridged complex 3 were successfully synthesized in the reaction of TiCl4 with a sodium salt of the appropriate ligand, and they were characterized by H-1 NMR spectroscopy. The ligands had either a dimethylamino side-arm donor and t-Bu substituents on both (1a) and one (1d) phenolate rings or a diisopropylamino side-arm donor and t-Bu (1b) and t-Bu along with OMe (1c) phenolate substituents. All complexes upon activation with [Ph3CB(C6F5)(4)] and MAO were used to catalyze polymerization of 1-octene (in liquid monomer) into poly(1-octene). Their activities as well as product microstructures were found to be highly dependent on the structure of the diamine-bis(phenolate) ligand. The catalytic activities of the complexes towards 1-olefin polymerization decreased in the following order: 2a >> 2b >2c >2d. The polymers produced were atactic or isotactic with the [mmmm],pentad content varied from about 4 up to 90%. The highest isotacticity was exhibited by poly(1-octene) synthesized by 2d. The catalytic activities increased and polymer molecular weight decreased with the increasing reaction temperature. Moreover, catalyst 2a/Al(iBu)(3)Ph3CB(C6F5)(4) was used in the bulk polymerization of other alpha-olefin and it was found that the monomer conversion decrease in the order: 1-octene > 1-decene > 1-dodecene >1-hexene >> 4-methyl-1-pentene. (C) 2016 Elsevier B.V. All rights reserved.