dVinyl-type random and block copolymerizations of norbornene with conjugated dienes such as isoprene and 1,3-butadiene were explored using a series of nickel compound/MMAO [modified methylaluminoxane, (AlMeO)(n)/(Ali-BuO)(m) = 3:1] systems as a cocatalyst at 25 degreesC for 12 h, or 25 degreesC for 6 h followed by the reaction at 60 degreesC for 12 h, respectively, in chlorobenzene. The catalysts used here are nickel compounds bearing a N- or O-donated ligand such as bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine-nickeI bromide (1), 4,4',4"-tri-t-butyl-2,2':6',2"-terpyridine-nickel chloride (2), m-xylylenedi{bis[2-(2-pyridyl)ethyl]} amino-nickel bromide (3), N,N-dibenzyl-N-2-pyridylmethylamino-nickel bromide (4), nickel-tropolonoide (5), and nickel-1,3-diphenyl-1,3-propanedionate (6) coupled with MMAO. All of these catalyst systems are highly active for the vinyl-type polymerization of norbornene, while only 5 and 6 is active for the homopolymerization of 1,3-butadiene and for random and block copolymerizations of norbornene with 1,3-butadiene. The molecular structures of 2, 4, and 6 were determined by X-ray analyses. (C) 2004 Elsevier B.V. All rights reserved.