The reaction of Li-2[Me2Si(3-R-C5H3)(2)] salts with Zr{Me3SiN(CH2)(3)NSiMe3}Cl-2(THF)(2) in THF quantitatively afforded rac-Me2Si(3-R-C5H3)(2)Zr{Me3SiN(CH2)(3)NSiMe3} zirconocenes with 100% stereoselectivity. NMR monitoring studies showed that these reactions initially form rac/meso mixtures, which undergo isomerization to pure rac. The isomerization requires Cp-enantioface exchange and is catalyzed by chloride ion, which reversibly displaces Cp- from Me2Si(3-R-C5H3)(2)Zr{Me3SiN(CH2)(3)NSiMe3}. Kinetic analyses for selected complexes showed first-order dependence of the isomerization rate on both metallocene and chloride concentrations. Reversible Cp-/Cl- exchange is also facile for {ansa-bis-Cp}ZrCl2 and nonbridged Cp2ZrCl2 complexes.