Achieving strictly linear polyethylenes by the <i>NNN</i>‐Fe precatalysts finely tuned with different sizes of <i>ortho</i>‐cycloalkyl substituents

Abstract

Six examples of newly synthesized α,α’‐bis (aryl)‐2,3:5,6‐bis (pentame thylene)pyridyliron complexes [2,3:5,6‐{C 4 H 8 C(NAr)} 2 C 5 HN]FeCl 2 (Ar = 2‐( c ‐C 5 H 9 )‐6‐MeC 6 H 3 Fe1 , 2‐( c ‐C 6 H 11 )‐6‐MeC 6 H 3 Fe2 , 2‐( c ‐C 8 H 15 )‐6‐MeC 6 H 3 Fe3 , 2‐( c ‐C 5 H 9 )‐4,6‐Me 2 C 6 H 2 Fe4 , 2‐( c ‐C 6 H 11 )‐4,6‐Me 2 C 6 H 2 Fe5 , 2‐( c ‐C 8 H 15 )‐4,6‐Me 2 C 6 H 2 Fe6 ; c refers as cyclic), on activation with methylalumoxane (MAO) or modified MAO (MMAO), exhibit high activities towards ethylene polymerization, producing strictly linear polyethylenes with terminal vinyl groups. The catalytic performances are systematically investigated along with various polymerization parameters as well as the microstructures of resultant polyethylenes. The steric hindrances of ortho ‐cycloalkyl substituents of N imino ‐aryl groups significantly affect the activities of the corresponding iron precatalysts as well as the microstructures of resultant polyethylenes: higher steric hindrance the ortho ‐cycloalkyl substituents, higher activity the iron precatalyst, lower molecular weight the resultant polyethylenes. Experimental observations are additionally supported by the computational study. The resultant polyethylenes exhibited excellent hydrophobicity.