Dissymmetric bis(indenyl) Zirconium Dichloride Complexes as Catalyst Precursors for Homogeneous Ethylene Polymerization

Six new dissymmetric bis(indenyl) zirconium dichloride complexes of the type (C9H7)[C9H6-(CH2)n-O-Ar]ZrCl2 (n = 3-5; Ar = aryl group) bearing an unsubstituted and an ω-aryloxyalkyl substituted indenyl ligand were synthesized, characterized, activated with methylalumoxane (MAO) and tested for ethylene polymerization. The activities of the catalysts depend very much on the steric bulk of the O-Ar group as well as on the CH2- chain length between the aryloxy group and the indenyl ligand. The best activity (26233 kg PE/mol cat h) was obtained with catalyst precursor 4a (n = 3; Ar = 2- biphenyl). Obviously the biphenyl group and the limited length of the CH2-chain protect the oxygen atom very efficiently from coordination to an active site of the same or a neighboured molecule during the polymerization process.