The effects of polymerization temperature, polymerization time, ethylene and hydrogen concentration, and. effect of comonomers (hexene-1, propylene) on the activity of supported catalyst of composition LFeCl2/MgCl2-Al(i-Bu)(3) (L = 2,6-bis[1(2,6-dimethylphenylimino)ethyl] pyridyl) and polymer characteristics (molecular weight (MW), molecular-weight distribution (MWD), molecular structure) have been studied. Effective activation energy of ethylene polymerization over LFeCl2/MgCl(2)AI(i-BU)(3) has a value typical of supported Ziegler-Natta catalysts (11.9 kcal/mol). The polymerization reaction is of the first order with respect to monomer at the ethylene concentration >0.2 mol/L. Addition of small amounts of hydrogen (9-17%) significantly increases the activity; however, further increase in hydrogen concentration decreases the activity. The IRS and DSC analysis of PE indicates that catalyst LFeCl2/MgCl2-Al(i-Bu)(3) has a very low copolymerizing ability toward propylene and hexene-1. MW and MWD of PE produced over these catalysts depend on the polymerization time, ethylene and hexene-1 concentration. The activation effect of hydrogen and other kinetic features of ethylene polymerization over supported catalysts based on the Fe (II) complexes are discussed. (c) 2007 Wiley Periodicals, Inc.