Journal of Natural Gas Chemistry 12(2003)98{104 Nickel Complexes Bearing Bidentate Schi Base as Ethylene Oligomerization

N2) were synthesized. Some of the nickel complexes exhibit high activity for ethylene oligomerization in the presence of an organoaluminum activator. The main factor aecting the activity and the structure of oligomers is the steric eect of substituents on [N,N] ligands. Methylaluminoxane (MAO)-activated catalysts showed higher activities and produced oligomers with higher molecular weight than Et2AlCl-activated ones. The oligomerization in toluene rather than hexane results in much higher activity, and the oligomers produced in toluene have relatively high molecular weight. With activation of MAO or Et2AlCl, the [N,N]NiBr2 system tended to produce highly branched oligomers with low -olen content, but the -ole n content could be increased by changing the reaction conditions. Key words: nickel complexes, Schi base, ethylene, oligomerization 1