beta-Diketiminato complexes Ni{(N(Ar)C(Me))(2)CH}Br (9), Ni{(N(Ar)C(Me))(2)CH} Pph(3)Br (10) and P-diimine complexes Ni{(N(Ar)C(Me))(2) CH2}Br-2 (5) (Ar = 2,6-iPr(2)C(6)H(3) (a), 2,6-Me2C6H3 (b)) were used as catalyst precursors for ethylene polymerization in the presence of methylaluminoxane (MAO). High molecular weight ethylene polymers as well as short chain oligomers (C4-C8) were simultaneously produced from the catalysis reactions. Ethylene polymers obtained by using these beta-N-N Ni(H)IMAO catalyst systems are mainly methyl branched. Small amounts of even number branches were also observed in the C-13 NMR spectra of the obtained ethylene polymers, which are believed generating from the incorporation of simultaneously produced alpha-olefins. Except methyl branch and the branches derived from the incorporation of alpha-olefin oligomers, the formation of other branch types via the chain walking process is not favored in beta-diketiminato Ni(II) systems. (c) 2006 Elsevier B.V. All rights reserved.