Novel double silylene-bridged binuclear Group 4 metallocene complexes [(eta(5)-C(5)H(5)) MCl(2)](2)[mu, mu(SiMe(2))(2) (eta(5)-RC(5)H(2))(2)] [R = Me, M Zr (1); R allyl, M = Ti (2); R allyl, M Zr (3); R (n)Bu, M = Ti (5); R = Me(3)Si, M Zr (6)] and [(eta(5)-CH(3)C(5)H(4))ZrCl(2)](2)[mu, mu-(SiMe(2))(2) (eta(5)-allyl-C(5)H(2))(2), (4)] were synthesized by the reaction of CpMCl(3) (M = Ti, Zr) with [mu, mu-(SiMe(2))(2) (eta(5)-RC(5)H(2))(2)](2-) (L(2-)) in THF, and they were all well characterized by (1)H-NMR, MS, and EA. When activated with methylaluminoxane (MAO), this series complexes are active catalysts for Ethylene polymerization (Complex 3, 3.86 x 10(6) g-PE/mol-M h, Al/Zr = 500) and copolymerization of ethylene with 1-hexene (Complex 3,30.87 x 10(5) g-polymer/mol-M h, 1-hexene content in polymer 2.34 mol %, Al/Zr = 1000). The result of polymerization implies that there is a cooperative effect between the two metals in the double-bridged binuclear molecules. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 21-26, 2011