A family of unsymmetrical 1,2-bis(imino)acenaphthene-palladium methyl chloride complexes [1-[2,6-{(C6H5)(2)CH}(2)- 4-{C(CH3)(3)}-C6H2N]-2-(ArN)C2C10H6]PdMeCl (Ar=2,6-Me2Ph Pd1, 2,6-Et2Ph Pd2, 2,6-(Pr2Ph)-Pr-i Pd3, 2,4,6-Me3Ph Pd4, 2,6-Et-2-4-MePh Pd5) have been prepared and fully characterized by H-1/C-13 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 kgmol(-1). (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 922-930