摘要：

A new linked bis(cyclopentadienyl) ligand [(C{sub 5}H{sub 3}-2-SiMe{sub 3}-4-CMe{sub 3}){sub 2}Si(OC{sub 10}H{sub 6}C{sub 10}H{sub 6}O)] (BnBpH{sub 2}), has been designed to coordinate to transition metals to afford a single enantiomeric C{sub 2}-symmetric ansa-metallocene. The syntheses of its dipotassium salt and (BnBp)YCl(THF) are described. Steric interactions between the 3- and 3`-methine positions of the 1,1`-binaphth-2,2`-diolate rings of the chiral linker with the $alpha@-trimethylsilyl substituents on the cyclopentadienyl rings force enantioselective metalation of this ligand. Thus, coordination to yttrium occurs in an entirely diastereoselective manner: the ligand prepared from (R)-(+)-1,1`-bi-2-naphthol directs formation of the (S)-yttrocene, (R,S)-(BnBp)YCL(THF), while that from (S)-(-)-1`1-bi-2-naphthol directs formation of the (R)-yttrocene, (S,R)-(BnBp)YCl(THF). Removal of coordinated tetrahydrofuran allows the preparation of (BnBp)YCH(SiMe{sub 3}){sub 2}. Treatment of rac-(BnBp)YCH(SiMe{sub 3}){sub 2} with H{sub 2} yields a kinetic mixture of both heterochiral and homochiral dimers e.g. (R,S)-(BnBp)Y({mu}{sub 2}-H){sub 2}-(S,R)-(BnBp) and (R,S)-(BnBp)Y({mu}{sub 2}-H){sub 2}-(R,S)-Y(BnBp), respectively. Over several hours this mixture undergoes conversion to the pure homochiral dimers. As anticipated, hydrogenolysis of enantiopure (BnBp)YCH(SiMe{sub 3}){sub 2} (e.g. R,S-(BnBp)YCH(SiMe{sub 3}){sub 2}) affords directly only enantiopure homochiral dimer. 38 refs., 4 figs., 1 tab.

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