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Synthesis of C7,C7‘-Ethylene- and C7,C7‘-Methylene-Bridged C2-Symmetric Bis(indenyl)zirconium and -titanium Dichlorides

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journal contribution
posted on 05.08.1998, 00:00 authored by Ronald L. Halterman, David Combs, Masood A. Khan
We have prepared several novel metallocenes bridged at the 7,7‘-positions of the indenyl moiety. The new metallocenes include the methylene-bridged [dl-bis(4,6-dimethylinden-7-yl)methylidene]titanium dichloride (20) and [dl-bis(4,6-dimethylinden-7-yl)methylidene]zirconium dichloride (21), which were prepared from m-xylene. In addition, [dl-1,2-bis(4-methylinden-7-yl)ethylidene]- and [dl-1,2-bis(4-isopropylinden-7-yl)ethylidene]zirconium dichlorides (dl-12a and dl-12b) and [dl-1,2-bis(4-isopropylinden-7-yl)ethylidene]titanium dichloride (dl-13) were synthesized from p-cymene and p-xylene, respectively. The structures of metallocene dichlorides dl-12a, dl-12b, and dl-13 were determined by X-ray crystallography and found to have C1 symmetry in the solid state but in solution exhibit C2 symmetry, as seen in the 1H NMR spectra at room temperature.