The behavior of homogeneous iron-based catalysts bearing pyridine diimine ligands for ethylene polymerization

The polymerization of ethylene by two iron-based catalysts, {[2,6-ArN=C(Me) (2)C5H3N]FeCl2} (Ar = 2,6-C6H3-Me-2 I; 2,6-C6H3 (i-Pr)(2) II) has been inve stigated. Catalyst II produces higher molecular weight polyethylene (PE) an d broadened polydispersities relative to catalyst I under analogous conditi ons and all polymers are linear. The kinetic profiles with iron catalysts s howed a smooth pattern during both rate build-up and rate lowering, which a re different from the metallocene catalysts. The polymerization activity in creases with Al/Fe value and an optimum temperature range at 40 similar to 45 degreesC was observed. The molecular weight of PE decreases with the inc rease of Al/Fe ratio and rise of polymerization temperature.