Zirconium complexes as catalysts for the oligomerisation of ethylene: The role of chelate ligands and the Lewis acid cocatalyst in the generation of the active species

Abstract

Highly effective catalysts for the conversion of ethylene into linear α-olefins may be generated in situ from zirconium tetrachloride, a β- aminoketone or β-aminothioketone ligand and an alkylaluminium chloride Lewis acid cocatalyst. Catalysts may also be generated from ZrCl4 · 2HL adducts (where HL = monodentate, oxygen-bound β-aminoketones), and from bis-ligand complexes of the type ZrCl2L2 (where L = monovalent, bidentate β- aminoketones or β-aminothioketones) on treatment with an alkylaluminium chloride cocatalyst. Product distribution and catalyst activity can be adjusted by ligand substituent variation and/or by the method of catalyst formation. Catalyst systems generated from preforme..