A new series of palladium complexes (Pd1-Pd5) ligated by symmetrical 2,3-diiminobutane derivatives, 2,3-bis[2,6-bis{bis(4-FC6H4)(2)CH}(2)-4-(alkyl)C6H2N]C4H6 (alkyl=Me L1, Et L2, Pr-i L3, Bu-t L4) and 2,3-bis[2,6-bis{bis(C6H5)(2)CH}(2)-4-{(CH3)(3)C}C6H2N]C4H6 L5, have been prepared and well characterized, and their catalytic scope toward ethylene polymerization have been investigated. Upon activation with MAO, all palladium complexes (Pd1-Pd5) exhibited good activities (up to 1.44 x 10(6) g (PE) mol(-1)(Pd) h(-1)) and produced higher molecular weight polyethylene in the range of 10(5) g mol(-1) with precise molecular weight distribution (M-w/M-n=1.37-1.77). One of the long-standing limiting features of the Brookhart type -diimine Pd(II) catalysts is that they produce highly branched (ca. 100/1000 C atoms) and totally amorphous polymer. Conversely, herein Pd5 produced polymers having dramatically lower branching number (28/1000) as well as improved melting temperature up to 73.1 degrees C showing well-controlled linear architecture, and very similar to polyethylene materials generated by early-transition-metal based catalysts. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3214-3222