Ethylene Polymerization at High Temperatures Catalyzed by Double-Decker-Type Dinuclear Iron and Cobalt Complexes: Dimer Effect on Stability of the Catalyst and Polydispersity of the Product

Dinuclear Fe and Co complexes with a double-decker structure were synthesized by using macrocyclic ligands having two bis(imino)pyridine groups. X-ray crystallography of the dinuclear Co complex revealed that the two bis(imino)pyridine Co moieties stack in an antiparallel manner with a distance of 7.74 Å. A dinuclear Fe complex catalyzes ethylene polymerization at 80–120 °C (5 atm ethylene) to produce polymers with a relatively narrow molecular weight distribution ( M w / M n = 1.75–2.77); its highest activity is 975 g (mmol Fe) −1 h –1 atm –1 at 100 °C. Ethylene polymerization at room temperature under 1 atm ethylene catalyzed by the dinuclear Co and Fe complexes produces polymers with much higher molecular weight ( M n up to 15.5-fold increase) than the corresponding mononuclear complexes.