Catalytic Performance of Pentacoordinate Iron(II) Complexes with Modified Bis(imino)pyridine Ligands for Ethylene Oligomerization

A series of new 2,6-bis(imino)pyridyl ligands was prepared and fully characterized using a range of analytical techniques. 2D NMR spectroscopy and infrared spectroscopy were used to understand the effects of the substituents on the electronic characteristics of the ligands. The reaction of these ligands with anhydrous FeCl ₂ afforded pentacoordinate Fe(II) complexes C1-C12 . The FT-IR spectra of these complexes confirmed the coordination of the BIP ligand via the nitrogen donor atoms. In addition, the molecular compositions of the complexes were confirmed by mass spectrometry and elemental analysis. The magnetic susceptibility of the complexes was consistent with a five-coordinate metal center, with an iron metal center in the 2 + oxidation state. All the new Fe (II) BIP complexes C3-C6 and C9-C12 , when activated with MMAO at 60°C and 5 atm, were found to be active catalysts for ethylene oligomerization; however, very low activity was observed. The ligand environment directly influenced the activity and selectivity of the catalyst.