New double silylene-bridged binuclear zirconium complexes [(eta(5)-RC5H4)ZrCl2](2)[mu,mu-(SiMe2)(2)(eta(5)-C5H3)(2)] [R = H (1), Me (2), Pr-n (3), Pr-i (4), Bu-n (5), allyl (6), 3-butenyl (7), benzyl (8), PhCH2CH2 (9), MeOCH2CH2 (10)] were synthesized by the reaction of (eta(5)-RC5H4)ZrCl3 center dot DME with [mu,mu-(SiMe2)(2)(eta(5)-C5H3)(2)](2-) (L2-) in THF, and they were all well characterized by H-1 NMR, MS, IR, and EA. The binuclear structure of Complex 3 was further confirmed by X-ray diffraction, where the two zirconium centers are located trans relative to the bridging [mu,mu-(SiMe2)(2)(eta(5)-C5H3)(2)] moiety. When activated with methylaluminoxane (MAO), this series of zirconium complexes are highly active catalysts for the polymerization of ethylene even under very low molar ratio of Al/Zr (Complex 7, 5.41 X 10(5) g-PE/mol-Zr center dot h, Al/Zr = 50) and linear polyethylenes (PEs) with broad molecular weight distribution (MWD, M-w/M-n = 7.31-27.6) was obtained. The copolymerization experiments indicate that these complexes are also very efficient in the incorporation of 1-hexene into the growing PE chain in the presence of MAO (Complex 6, 3.59 X 10(6) g-PE/mol-Zr-h; 1-hexene content, 3.65%). (c) 2007 Wiley Periodicals, Inc.