Vinyl-type polymerizations of norbornene and styrene as well as random copolymerizations of norbornene with styrene were examined using a series of nickel compound/MMAO [modified methylalurnoxane, (AlMeO)(n)/(Ali-BuO)(m) = 3: 1] systems as catalysts at 25 degreesC for 12 It in chlorobenzene. The catalysts used here are nickel compounds bearing a N- or O-donated ligand such as bis[1-(2,6-dimethylphenylimino)ethyl]pyridine-nicket bromide (1), bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine-nickel bromide (2), 2,2':6',2"-terpyridine-nickel chloride (3), nickel-tropolonoide (4), nickel-4-iPr-tropolonoide (5), nickel- 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate (6), and nickel-2,2,6,6-tetramethyl-3,5-heptadionate (7) coupled with MMAO. All of these catalyst systems are highly active for the vinyl-type polymerization of norbornene, while only 4 and 6 are active for the homopolymerization of styrene and for random copolymerizations of norbornene with styrene. We failed in the random copolymerizations of norbornene with methyl methacrylate (MMA) or E-caprolactone (CL). We have also demonstrated the random vinyl-type copolymerizations of norbornene with polar norbornene derivatives. The molecular structures of 1, 2, 3 and 4 were determined by X-ray analyses. (C) 2003 Elsevier B.V. All rights reserved.