Ni(acac)2-DAD/MAO : A new catalytic system for ethylene polymerization

The halide-free combination of Ni(acac) 2 and DAD(diazadiene, ArN=CH-CH=NAr, where Ar = 2,6-C 6 H 3 (i-Pr) 2 ) is active for ethylene polymerization in the presence of methylaluminoxane (MAO). The performance of this new catalytic system was evaluated with respect to activity and polymer structure. The degree of branching of the obtained polyethylenes is substantially influenced by the polymerization conditions. The activation mechanism was investigated by 'H NMR. MAO is proposed to participate in the ligand exchange process.