Synthesis of Enantiomerically Pure Ethylene-Bridged ansa-Zirconocene and -Hafnocene Complexes Bearing Fluorenyl, Indenyl, Octahydrofluorenyl, and Tetrahydroindenyl Ligands1

We report on an efficient synthetic route for the preparation of enantiomerically pure ethylene-bridged ansa -zirconocene and -hafnocene complexes, bearing different cyclopentadienyl fragments. Ring opening of ( R )-epoxystyrene ( 1 ) with fluorenyllithium proceeds enantiospecifically and leads to optically pure 2-(9-fluorenyl)-1-( S )-phenylethanol ( 2a ) and 2-(9-fluorenyl)-2-( S )-phenylethanol ( 2b ) in nearly quantitative yield. Treatment of 5, the trifluoromethanesulfonate derivative of 2b, with fluorenyl- and indenyllithium results in the formation of 1-(9-fluorenyl)-1-( S )-phenyl-2-(1-indenyl)ethane ( 6a ) and 1,2-bis(9-fluorenyl)-1-( S )-phenylethane ( 6b ), respectively. Reaction of the dilithio salts of 6a with ZrCl 4 and of 6b with MCl 4 (M = Zr, Hf) affords the formation of the enantiomerically pure complexes [1-(η 5 -9-fluorenyl)-1-( R )-phenyl-2-(η 5 -1-( R, S )-indenyl)ethane]ZrCl 2 ( 7a = R, R; 7b = R, S ) and of [1,2-bis(η 5 -9-fluorenyl)-1-( R )-phenylethane]MCl 2 ( 7c, M = Zr; 7d, M = Hf) in up to 63% yield. Hydrogenation of 7a − d with H 2 /PtO 2 gives the complexes 8a − d, bearing octahydrofluorenyl and tetrahydroindenyl ligands. Hydrolysis of 8a, b in basic, aqueous media leads to the formation of C 2 -symmetric μ-oxo dimers ( 12a, b ). The solid-state structures of enantiomerically pure 7b and 8c and of 12b are reported.