A variety of iron complexes bearing tridentate pyridine based ligands are presented as highly active precatalysts for the oligomerization and polymerization of ethene and propene. The ligands comprise two classes:  the first class, where both ketone groups of the 2,6-diacetylpyridine are converted to imines to give symmetrical or unsymmetrical bis(imino)pyridines (NNN ligands; 1−4, 8, and 9), and the second class, where only one keto function of the 2,6-diacetylpyridine is substituted by an imine to give monoiminoacetylpyridines (NNO or MIAP ligands; 5−7). The NNN ligands have been reacted with FeCl2·4H2O to afford the corresponding metal complexes (12−17). These complexes have been activated by modified methylaluminoxane (MMAO) and tested in the oligomerization and polymerization reaction of ethene and propene. Depending on the steric bulk of the ortho substituents at the aryl group of the imines, tunable polymerization products are observed, with molecular weights (M w) of 102−106. Using the MIAP ligands, complexes of Co(II), Cr(II), Fe(II), Mn(II), and Ni(II) (18−24) have been prepared. The solid-state X-ray structures of the square-pyramidal {2-acetyl-6-[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}metal halide complexes 18, 21, and 22b (M = Co(II), Fe(II), Ni(II)) have been compared. Additionally, the solid-state structure of {2,6-bis[1-(1-biphenylimino)ethyl]pyridine}iron(II) chloride (15) is presented. All ligands and complexes have been characterized by spectroscopic methods, mass spectra, and elemental analysis.

The well-known catalyst precursor 2,6-bis[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine (1) is functionalized by various alkenyl groups to yield the corresponding alkenyl-functionalized 2,6-bis[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine ligand. Reaction of these novel functionalized bis(imino)pyridyl ligands with iron(II) chloride results in the formation of precatalysts 5−7, which possess different spacer moieties. The possibility of self-immobilization has been investigated with respect to the chain length of the alkenyl moiety. Additionally, experiments to heterogenize these functionalized iron(II) complexes on modified silica via hydrosilation are presented (8−10). The immobilization has been studied by IR, and the resulting polymers have been characterized by GPC and static light scattering.

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