Highly active and selective ethylene oligomerization catalysts: Asymmetric 2,6-bis(imino)pyridyl iron (II) complexes with alkyl and halogen substitutients

A series of asymmetric 2,6-bis(arylimino)pyridines with alkyl and halogen substitutients on different iminoaryl rings and corresponding iron (II) complexes ([2-(Ar1N = CCH3)-6-(Ar2N = CCH3)C5H3N]FeCl2, 3a–3j) are synthesized and characterized. These Fe(II) complexes are highly active for ethylene oligomerization with high selectivity for linear α-olefins. The oligomer distributions can be tuned by the synergism of alkyl-steric effect and halogen electronic effect, and the production of C6–C16 can reach more than 80% with the highest selectivity being 87.5% for 3 g (Ar1 = 2-ethylphenyl, Ar2 = 2-fluorophenyl), which is 15–30% higher than that catalyzed by their methyl or fluoro-substituted symmetric counterparts.

Graphical abstractA series of asymmetric bis(arylimino) pyridyl iron complexes with alkyl and halogen substitutients on different iminoaryl rings of ligands are synthesized and characterized. These complexes were found to catalyze ethylene oligomerization with high activity and led to the augmentation of the more useful C6–C16 portion.Figure optionsDownload full-size imageDownload as PowerPoint slide