A new series of nitro-substituted bis(imino)pyridine ligands [2,6-bis[1-(2-methyl-4-nitrophenylimino)ethyl]pyridine, 2,6-bis[1-(4-nitrophenylimino)ethyl]pyridine, (1-16-[1-(4-nitro-phenylimino)-ethyl]-pyridin-2-yl]-ethylidene)-(2,4,6-t rimethyl-phenyl)-amine, and 2,6-bis[1-(2-methyl-3-nitrophenylimino)ethyl]pyridine} and their corresponding Fe(II) complexes [{p-NO2-o-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-Me-p-NO2)FeCl2 (10), L2FeCl2 (11), [m-NO2-o-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-Me-m-NO2)FeCl2 (12), and {p-NO2-Ph-N=C(Me)-Py-C(Me)=N-Mes} FeCl2 (14)] were synthesized. According to X-ray analysis, there were shortenings of the axial Fe-N bond lengths (up to 0.014 angstrom) in para-nitro-substituted complex 10 and (up to 0.015 angstrom) in meta-nitro-substituted complex 12 versus the Fe(II) complex without nitro groups [{o-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-M}FeCl2 (1)], Complexes 10, 12, and 14 afforded very active catalysts for the production of alpha-olefins and were more temperature-stable and had longer lifetimes than parent non-nitro-substituted Fe(II) complex 1. The reaction between FeCl2 and a sterically less hindered ligand [p-NO2-Pb-N=C(Me)-Py-C(Me)=N-Ph-p-NO2] resulted in the formation of octahedral complex 11. A para-dialkylamino-substituted bis(imino)pyridine ligand [p-NEt2-o-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-Me-p-NEt2] and the corresponding Fe(II) complex [[{p-NEt2-o-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-Me-p-NEt2)FeC]2 (16)] were synthesized to evaluate the effect of enhanced electron donation of the ligand on the catalytic performance. According to X-ray analysis, there was a shortening (up to 0.043 angstrom) of the axial Fe-N bond lengths in para-diethylamino-substituted complex 16 in comparison with parent Fe(II) complex 1. (c) 2006 Wiley Periodicals, Inc.