Series of Fe(II) and Fe(III) tridentate bis(imino)pyridine complexes without nitrilo groups 2-6 and with nitrilo groups 7-13 were, synthesized. According to X-ray analysis, the introduction of nitrilo groups in para- and ortho-positions tends to result in shorter axial Fe-N bonds. Both types of complexes, 2-6 and 9-13, afforded very productive catalysts for the production of alpha-olefins with higher K values and better linearity of Schultz-Flory distribution alpha-olefins than the parent methyl substituted Fe(II) complex 1. Noticeably, the complexes functionalized with a para-nitrilo group 9-13 tend to make alpha-olefins with higher K values of the Schultz-Flory distribution, more ideal distributions, and less of the heavier insoluble fractions of alpha-olefins than corresponding nonsymmetrically substituted complexes without para-nitrilo groups 2-6. Statistically significant correlations were obtained between % solids of total alpha-olefins and the blocked solid angle fraction in the +z hemisphere (R-adj(2) = 51.3%, p = 0.012) and between catalyst productivity and total blocked solid angle fraction (R-adj(2) = 43.5%, p = 0.023). The modest values of R2 determinadi R-adj(2) show that, while steric effects are significant, they are not the sole factor Ing catalyst performance. (C) 2007 Wiley Periodicals, Inc.