Synthesis, structures and catalytic properties of Group 4 metallocenes based upon [Me2E(C5H4)(C5Me4)]2 (E=Si, Ge) supporting coordination

The ansa-metallocene complexes Me2Si(η5-C5H4)(η5-C5Me4)MCl2 [M=Ti (1), Zr (2), Hf (3)] were prepared by the reaction of [Me2Si(η5-C5H4)(η5-C5Me4)]Li2 with MCl4·2THF. Complexes Me2Ge(η5-C5H4)(η5-C5Me4)MCl2 [M=Ti (4), Zr (5)] were synthesized using similar method from the germyl-bridged ligand. The molecular structures of 1–3 and 5 have been determined by X-ray diffraction. Complexes 1–3 and 5 in combination with MAO were studied as catalysts for ethylene polymerization and it was found that zirconocene catalysts show much higher activities than the titanocene and hafnocene and the activities reach the maximum at high temperature. This indicates that the zirconocene system based upon [Me2E(C5H5)(C5Me4)]2 (E=Si, Ge) supporting coordination is a highly stable ethylene polymerization catalyst system. The relationship between structures and catalytic properties of catalysts is discussed.