Ethylene polymerization in the presence of iron(II) 2,6-bis(imine)pyridine complex: Structures of key intermediates

The structures of intermediates generated by the activation of 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridineiron(III) chloride(1) with various cocatalysts, methylalumoxane (MAO), trimethylaluminum (TMA), and TMA in combination with B(C6F5)(3) and Ph3CB(C6F5)(4), is studied by H-1 and H-2 NMR spectroscopy. The 1/AlMe3 system exhibits a higher catalytic activity in ethylene polymerization than the 1/MAO system, The activity of the latter decreases sharply with a decrease in the amount of AlMe3 in MAO. Neutral Fe(II) complexes rather than cationic intermediates are suggested to be active components in both catalytic systems.