A family of unsymmetrical 1,2-bis(imino)acenaphthene-palladium methyl chloride complexes [1-[2,6-{(C 6 H 5 ) 2 CH} 2 -4-{C(CH 3 ) 3 }-C 6 H 2 N]-2-(ArN)C 2 C 10 H 6 ]PdMeCl (Ar 5 2,6-Me 2 Ph Pd1, 2,6-Et 2 Ph Pd2, 2,6-i Pr 2 Ph Pd3, 2,4,6-Me 3 Ph Pd4, 2,6-Et 2 -4-MePh Pd5) have been prepared and fully characterized by 1 H/ 13 C NMR, FTIR spectroscopies, and elemental analysis. X-ray diffraction analysis of Pd2 complex revealed a square planar geometry. Upon activation with methylaluminoxane, all the palladium complexes displayed high activities for norbornene (NBE) homo-polymerization producing insoluble polymer. For the copolymerization of NBE with ethylene, Pd4 complex exhibited good activities with high incorporation of ethylene (up to 59.2-77.4%) and the resultant copolymer showed high molecular weights as maximum as 150.5 kg mol 21 . V C 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 922-930