Manganese(II) Complexes in Ethene Polymerization

Abstract

A series of manganese(II) dichloro complexes made in situ and bearing mainly various nitrogen ligands was studied with a parallel screening method in order to identify catalytically active complexes for ethene polymerization using methylaluminoxane (MAO) as a cocatalyst. From the series two of the most active octahedral manganese(II) complexes, those bearing tetradentate nitrogen ligands with chiral bridges, [N,N‘-bis(quinoline-2-methylene)diiminocyclohexane]MnCl2 (1) and {N,N‘-(6,6‘-dimethylbiphenyl-2,2‘-diyl)bis[(2-pyridyl)methyl]diimine}MnCl2 (2), were selected for more detailed studies. According to their solid-state structures, it is common for these C2-symmetric manganese complexes to have a distorted-octahedral coordination geometry where chlorides occupy cis positions with wide Cl−Mn−Cl angles (132−135°). The highest activity in ethene polymerization (67 kg of PE/((mol of Mn) h)) was obtained with 1/MAO at 80 °C. Furthermore, the alkylation of 1 and 2 with MeMgBr and (benzyl)MgBr was investigated, but only their monobenzyl derivatives were isolable.