Synthesis, structure and polymerization catalytic properties of doubly bridged bis(cyclopentadienyl) dinuclear titanium and zirconium complexes

A series of doubly bridged dinuclear titanium and zirconium complexes (Me2C)(Me2E)(C5H3)2(Cp′MCl2)2 [E=Si, Cp′=C5H5, M=Ti (1), Zr (2); E=Ge, Cp′=C5H5, M=Ti (3), Zr (4); Cp′=C5Me4H, M=Zr, E=Si (5), Ge (6)] and (Me2SiOSiMe2)2(C5H3)2(Cp′MCl2)2 [Cp′=C5H5, M=Ti (7), Zr (8); Cp′=C5Me4H, M=Zr (9)] were synthesized by the reaction of the lithium compounds of the corresponding doubly bridged cyclopentadienyl ligands with CpTiCl3, CpZrCl3(THF)2 or C5Me4HZrCl3, respectively. These complexes were characterized by 1H-NMR, MS and elemental analysis. The crystal structure of 4 was determined by the X-ray diffraction. Their catalytic properties for ethylene polymerization were also studied in the presence of MAO.