Disiloxane bridged binuclear titanocene catalysts for ethylene polymerization

Two tetramethyldisiloxanediyl bridged binuclear titanocenes Cl2CpTiCp * (CH3)(2)SiOSi(CH3)(2)Cp*TiCpCl2(Cp * = substituted cyclopendienyl, R = H in catalyst A, R = Si(CH3)(3) in catalyst B) have been synthesized by the reacting dilithium salts of Cp*(CH3)(2)SiOSi(CH3)(2)Cp* with CpTiCl3 in the yields of 42% and 51% respectively. Their catalysis behavior for the polymerization of ethylene under different conditions were investigated, and compared with mononuclear metallocene, cyclopentadienyl-titanium dichloride. The result showed that these two catalysts have a middle activity for ethylene polymerization. The MWD of the polyethylene were rather wide and the highest molecular weight was as high as 5.9 x 10(4) g/mol. Furthermore, catalyst B exhibited unexpected temperature dependence for ethylene polymerization.