Synthesis and characterization of Group 4 metallocene complexes with two disiloxanediyl bridges

Group 4 metallocene complexes with two disiloxanediyl bridges [μ,μ-(Me2SiOSiMe2)2(C5H3)2]ZrCl2 (3) and [μ,μ-(Me2SiOSiMe2)2(C5H3)2]HfCl2 (4) have been prepared by the reaction of MCl4 (M=Zr, Hf) with distannylated bis(cyclopentadienes), while the zirconium complex, 3, was subjected to a single-crystal X-ray diffraction study. The reaction of TiCl4 with two equivalents of doubly disiloxane bridged distannylated bis(cyclopentadienes) gives rise to the formation of the doubly bridged dinuclear titanocene [μ,μ-(Me2SiOSiMe2)2(C5H3)2][TiCl3]2 (5). Methylation and benzylation of the complex 3 results in [μ,μ-(Me2SiOSiMe2)2(C5H3)2]ZrMe2 (6) and [μ,μ-(Me2SiOSiMe2)2(C5H3)2]-Zr(CH2C6H5)2 (7), respectively, without complications. Furthermore, the dibridged zirconium compound 3 polymerizes ethylene very efficiently in the presence of methylaluminoxane with an activity of 5 ton of PE/[Zr] mol h atm.