In the presence of methylaluminoxane (MAO), ethylene polymerization was successfully performed with homobinuclear zirconocene complexes {[(C5H5)ZrCl2](C5H4CH2 C6H4CH2C5H4)[(C5H5)ZrCl2]; 3o, 4m, and 5p}, which were prepared conveniently by the reaction of disodium(phenylenedimethylene)dicyclopentadienide [C6H6(CH2C5HNa)(2)] with 2 equiv of (N-5-Cyclopentadienyl)trichlorozirconium dimethoxyethane (CpZrCl3(DME)) in tetrahydrofuran and characterized by H-1-NMR and elemental analysis. The effects of the polymerization parameters, such as the temperature, time, concentration of the catalyst, MAO/catalyst molar ratio, and isomeric difference of the homobinuclear metallocene complexes 3o, 4m, and 5p were studied in detail. The results showed that all three catalytic systems had moderate activities in ethylene polymerization and afforded polyethylene with relatively broad polydispersities. The catalytic activity of 4m was somewhat higher than that of 3o and 5p but lower than that of 4,4'-bis(methylene)biphenylene-bridged zirconocene catalysts; this indicated that the distance between the two metal centers was too short in comparison with a 4,4'-bis(methylene)biphenylene bridge to increase the catalytic activity. (c) 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2193-2198, 2006