New catalytic systems, composed of bis(imino)pyridine (2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (A1), methylene-bridged bis(imino)pyridine (A(2))), iron (III) acetylacetonate (Fe(acac)(3)) and methylaluminoxane (MAO), are highly active for ethylene polymerization. The performance of this new catalytic system was evaluated with respect to catalytic activity and polymer properties. The highest catalytic activity of Fe(acac)(3)-A(1)/MAO (catA) system and Fe(acac)(3)-A(2)/MAO (catB) system at optimum condition reaches 10.5 x 10(6) g PE.(mol Fe h)(-1) and 17.3 x 10(6) g PE.(mol Fe h)(-1), respectively. The product viscosity-average molecular weight (M,,) of two catalytic systems range from 0.40 to 8.7 x 10(5). GPC characterizations of PE obtained show that the PE has bimodal molecular weight distribution (MWD). C-13 NMR and DSC analysis of PE sample indicates that the PE is highly linear and crystalline. Analysis of UV-vis absorption spectra, ethylene polymerization results, and prepared polyethylene structures indicate that Fe(acac)(3)-bis(imino)pyridine/MAO catalytic system could generate same active species as bis(imino)pyridyliron catalytic systems. (C) 2007 Wiley Periodicals, Inc.