Modified pyridine-bis(imine) iron and cobalt complexes: Synthesis, structure, and ethylene polymerization study

In this paper, we describe the synthesis of two new pyridine-bis(imine)s {4-chloro-2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine and 2,6-bis[1-(2,6-dimethylcyclohexylimino)ethyl]pyridine} and their complexation with iron and cobalt dichloride. The solid-state structure of the iron complexes was solved and found to be very close to catalysts already described by Brookhart and Gibson. Their ability to polymerize ethylene was investigated after activation with MAO. It was thus shown that the substitution of the pyridine ring of the ligand is unfavorable: their catalytic activity is rather low. The replacement of the aromatic rings on the imine functions by dimethylcyclohexyl rings resulted in a complete loss of activity of the iron complex for oligomerization and polymerization of ethylene. With the cobalt analog, polymerization of ethylene could be achieved under the same conditions. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).