Bis(arylimino)pyridine iron(III) complexes as catalyst precursors for the oligomerization and polymerization of ethylene
A series of 26 bis(arylimino)pyridine iron(III) complexes containing either electron withdrawing or electron donating substituents in their ligand frameworks was synthesized and characterized. After activation with methylaluminoxane (MAO), these catalysts oligomerize or polymerize ethylene to give both linear and branched products. In contrast to iron(II) complexes, the presence of at least one ortho-substituent at the iminophenyl rings is not obligative for catalytic activities of the iron(III) complexes. A couple of such iron(III) complexes containing meta- and para-substituted bis(arylimino)pyridine compounds were accessible and their oligomerization behaviour revealed interesting differences to the well known iron(II) analogues since both internal and branched olefins were found in the product mixtures beside the expected linear α-olefins. The widths of the resulting molecular weight distributions and the degrees of isomerization of the resulting oligomers strongly depend on the substitution pattern at the ligand frameworks.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (114 K)Download as PowerPoint slideHighlights► Synthesis of new bis(arylimino)pyridine iron(III) catalyst precursors. ► The higher oxidation state of the metal center allows interesting modifications of the ligand frameworks. ► Very narrow product distributions were obtained in ethylene oligomerization reactions. ► “Open” ligand structures lead to internal and branched low molecular weight olefins.
Journal: Applied Catalysis A: General - Volume 403, Issues 1–2, 22 August 2011, Pages 25–35