Tuning High Temperature Performance Through Targeted Halide Substitution in a Bis(Imino)Pyridine‐Iron Ethylene Polymerization Catalyst

ABSTRACT Central to the function of an effective late transition metal ethylene polymerization catalyst is the interplay between electronic and steric factors in the ligand manifold. In this study, a family of meta ‐chloro‐substituted unsymmetrical bis(arylimino)pyridines, 2‐[CMe= N {4,6‐(CH( p ‐FPh)) 2 –3‐Cl‐2‐MePh}]‐6‐(CMe=NAr)C 5 H 3 N (Ar = 2,6‐Me 2 C 6 H 3 L1 , 2,6‐Et 2 C 6 H 3 L2 , 2,6‐ i Pr 2 C 6 H 3 L3 , 2,4,6‐Me 3 C 6 H 2 L4 , 2,6‐Et 2 ‐4‐MeC 6 H 2 L5 ), are employed as N,N,N ‐chelating ligand supports for their corresponding iron(II) chloride complexes, Fe1 – Fe5 . Besides their spectroscopic and analytical characterization, Fe5 and an oxo‐derivative of Fe3 , Fe3′ , have been the subject of single crystal XRD studies. Following activation with MAO, all five iron precatalysts exhibited exceptionally high activity for ethylene polymerization with appreciable lifetimes, with Fe1 the standout performer achieving a level of 18.6 × 10 6 g mol −1 h −1 at 80°C after 30 min and 53.9 × 10 6 g mol −1 h −1 over 5 min. To further showcase the thermal stability of Fe1 , the activity levels only decreased to 9.0 × 10 6 g mol −1 h −1 at 90°C and 3.2 × 10 6 g mol −1 h −1 at 100°C with the run time at 30 min. Furthermore, all catalysts generated highly linear polyethylene waxes ( M w range: 3–102 kg mol −1 ) with narrow dispersity ( M w / M n range: 1.9–4.1) and high levels of vinyl chain ends that could be influenced by the operating temperature. Such polymeric materials are integral to the development of functional polymers and serve as essential components in lubricant formulations.