Thio-imino-tetrahydroacridine Iron Complexes for Ethylene Polymerization

Abstract

A series of thio-imino-tetrahydroacridine iron complexes, (TITha)FeCl2, were synthesized and applied to ethylene polymerization. This class of NNS type iron complexes were designed by integrating a fused ligand backbone into our previously reported thio-imino-quinoline iron complexes (TIQ)FeCl2, with a major purpose to improve the thermal stability. Among the (TITha)FeCl2 series, complex 3c with ortho-Et substituents on the N-aryl ring exhibits high activity and thermal stability [up to 10.1 × 106 g of PE (mol of Fe)−1 h–1 at 50 °C and 2.3 × 106 g of PE (mol of Fe)−1 h–1 at 100 °C], producing highly linear low molecular weight polyethylene wax with narrow molecular weight distributions and unsaturated chain end. The comparison of catalytic behavior between (TITha)FeCl2 and (TIQ)FeCl2 indicates the modification of the tridentate ligand by introducing a more rigid backbone not only enhances the catalytic performance at high temperature but also exerts a significant impact on controlling the structures of the polymers.