Syntheses, characterizations, and olefin polymerizations of methylene-bridged 1,3-dimethylcyclopentadienyl/indenyl and 1,3-dimethylcyclopentadienyl/tetrahydroindenyl zirconium complexes

A cyclopentadiene compound having methyl substituents on 1,3-positions, 1,3-Me2-2-CH2(OTHP)-C5H3 (3) is prepared from 2-bromo-3-methyl-2-cyclopenten-1-one ethylene ketal (1) in 48% overall yield. Addition of 2.5 equivalents of indenyllithium to 3 affords a methylene bridged 1,3-dimethylcyclopentadienyl indenyl compound, CH2(1,3-Me2C5H3)(C9H7) (5) in 72% yield. Reaction of dilithium salt of 5 with ZrCl2(NMe2)2 (DME) furnishes an ansa-zirconocene complex [CH2(1,3-Me2C5H2)(C9H6)]Zr(NMe2)2 (6), which is transformed cleanly to the dichloride complex, [CH2(1,3-Me2C5H2)(C9H6)]ZrCl2 (7), by treatment of Me3SiCl. Hydrogenation of 7 over PtO2 gives a tetrahydroindenyl complex [CH2(1,3-Me2C5H2)(C9H10)]ZrCl2 (8). Reaction of the dilithium salt of 5 with Ti(NMe2)2Cl2 does not provide the desired ansa-titanocene complex, but a dinuclear complex [(1,3-Me2C5H2)Ti(NMe2)2Cl]–CH2–[(C9H6)Ti(NMe2)Cl] (9) is obtained. The solid structures of 6 and 9 were determined by X-ray crystallography. The ethylene and ethylene/norbornene (co)polymerizations were studied with 7/MAO and 8/MAO.