Methylaluminum dichloride as a cocatalyst for Ni(II) α-diimine complexes catalyzed ethylene polymerization

Abstract

Diimine Ni(II) catalysts have attained special interest due to their tunable polymerization activity and polymer microstructure by simple modification of the ligand architecture. 1,2 Technical process for olefin polymerization requires the use of suitable cocatalysts to transform inactive but readily prepared and handled catalyst precursors into the active species. The activity of methylaluminoxane (MAO) or its derivatives as cocatalysts is generally unmatched by other organoaluminum reagents. The ability of these substances to activate many kinds of catalytic precursors has been demonstrated for a wide range of transition metal catalyst precursors. However the practical use of MAO also poses some important drawbacks. For example, they are relatively expensive reagents that have to be used in large excess to achieve their optimum efficiency. Recently we have reported the polymerization/oligomerization behavior of late transition metal catalysts in combination with common alkyl aluminums like ethylaluminum sesquichloride (EAS). 3,4 In the present study we explore the use of methylaluminum dichloride (MADC) as a potential alternative for MAO towards the polymerization of ethylene with Ni(II) α-diimine catalysts.