The formation and polymerization behavior of Ni(II) α-diimine complexes using various aluminum activators

• Published in: Journal of organometallic chemistry 2002, Vol.645 (1), p.158-167
• Main Authors: Maldanis, Richard J, Wood, John S, Chandrasekaran, A, Rausch, Marvin D, Chien, James C.W
• Format: Article
• Language: English
• Subjects: Diimine; Nickel; Polyethylene; Polypropylene
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(01)01340-7

Several Ni(II) α-diimine complexes have been synthesized and examined for ethylene and propylene polymerization in combination with different aluminum co-catalysts. The precatalysts used in the study were [ArNC(Nap)C(Nap)NAr]NiBr 2 (Nap=1,8-naphthdiyl) ( 1, Ar=2,4,6-trimethylphenyl; 2, Ar =2- t Bu phenyl; 3, Ar=2- i Pr phenyl). These complexes were synthesized via a one-pot reaction where the ligand is formed via an acid catalyzed condensation followed by direct addition of nickel(II) bromide. The complexes were also prepared by a two-step procedure where the ligand was first formed by condensation between the appropriate aniline and acenaphthoquinone, and the resulting ligand was then allowed to react with (1,2-dimethoxyethane) nickel(II) dibromide. X-ray structural studies of complexes 1 and 2 have been carried out. Diethylaluminum chloride (DEAC), and 1,3-dichloro-1,3-diisobutyldialuminoxane (DCDAO) show higher activities for ethylene and propylene polymerizations in combination with these Ni(II) α-diimine complexes than does polymethylaluminoxane (MAO). The molecular weight of the resulting polymers as well as their respective polydispersities and T ms are also presented. The polypropylenes obtained with 1/DEAC and 2/DEAC at 0 °C show similar rr triad percentage as previously reported for polypropylenes generated by MAO activated Ni(II) α-diimine complexes. The formation and polymerization behavior of several Ni(II) α-diimine complexes ( 1– 3) are discussed. The complexes were synthesized via two different methods and these are presented as well as the X-ray structural studies of complexes 1 and 2. Polymerizations were carried out for ethylene and propylene with the use of 1– 3 in combination with various co-catalysts.