Transition Metal Complexes of Tetradentate and Bidentate Schiff Bases as Catalysts for Ethylene Polymerization: Effect of Transition Metal and Cocatalyst

摘要

This article compares catalytic performance of ethylene polymerization in similar polymerization conditions of transition metal complexes having two ligands [O,N] (phenoxy-imine) and having one tetradentate ligand [O,N,N,O] (salphen or salen). It is shown that the activity of both complex types as well as the product properties depend in the same way on the type of central metal in the complex and on the cocatalyst used. Although the type of ligand has some effect on the catalyst activity, yet it does not control the properties of the obtained products. The vanadium and zirconium complexes, irrespective of the cocatalyst used, yield linear polyethylene with high molecular weight (a few hundred thousand g/mol). Similar products are formed when titanium complexes activated with MAO are employed. On the other band, the same titanium complexes in conjunction with Et2AlCl, yield low molecular weight polyethylene (of a few thousand) and additionally a mixture of oligomers. (C) 2008 Wiley Periodicals, Inc. J Polyin Sci Part A: Polym Chem 47: 565-575, 2009