Two vanadium complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor, [V {Me2NCH2CH2N(CH2-2-O-3,5-tBu(2)-C6H2)(2)}Cl-2] (1) and [V(Me2NCH2CH2N(CH2-2-O-3,5-tBu(2)-C6H2)(CH2-2-O-C6H4)}Cl-2] (2), were synthesised and characterized by FTIR and H-1 NMR spectroscopy. Upon activation with Al(iBu)(3)/Ph3CB(C6F5)(4), these complexes became active catalysts for 1-octene polymerization giving highly stereoregular polymers (mmmm similar to 90%) having regioirregularly arranged units. The catalytic activity of the catalysts in ethylene homo- and copolymerization, and their ability to incorporate a comonomer were highly dependent on both the activator type and the complex structure. 1/EtAlCl2 exhibited very high activity (up to 3.3 center dot 10(7) g/(mol(v) h)) in ethylene polymerization and produced copolymers with the highest comonomer content (up to 9.1 mol%), moderate molecular weight and narrow chemical composition distribution (CCD). Both vanadium complexes, when combined with trityl borate activator, led to ethylene copolymers with lower 1-octene content and broad CCD. In addition, the copolymers were characterized by very high molecular weight (similar to 1 center dot 10(6) g/mol) and narrow dispersity (M-w/M-n= 1.4-2.0). (C) 2018 Elsevier Inc. All rights reserved.