A Convenient Method for the Synthesis of Zirconocene Hydrido Chloride, Isobutyl Hydride, and Dihydride Complexes Using tert-Butyl Lithium

Preparation of zirconocene hydrido chloride complexes has been accomplished via addition of 1 equiv of tert -butyllithium to the corresponding zirconocene dichlorides. In this manner, both Cp*Cp‘ ‘Zr(H)Cl and Cp‘ ‘ 2 Zr(H)Cl (Cp* = C 5 Me 5, Cp‘ ‘ = 1,3-(SiMe 3 ) 2 C 5 H 3 ) were prepared in high yield. Further addition of t BuLi to Cp*Cp‘ ‘Zr(H)Cl affords the isobutyl hydride complex Cp*Cp‘ ‘Zr(CH 2 CHMe 2 )(H), which upon addition of 1 atm of dihydrogen undergoes rapid hydrogenolysis yielding the monomeric dihydride Cp*Cp‘ ‘ZrH 2 . In the absence of dihydrogen, the zirconocene dihydride undergoes reversible C−H activation of a cyclopentadienyl trimethylsilyl group, affording the “tuck-in” derivative Cp*(η 5 -1-SiMe 3 C 5 H 3 -3-(η 1 -SiMe 2 CH 2 ))ZrH. Addition of 2 equiv of t BuLi to the ansa -zirconocene i Pr 2 Si(η 5 -3-SiMe 3 C 5 H 3 )(η 5 -3,4-(SiMe 3 ) 2 C 5 H 2 )ZrCl 2 results in the corresponding zirconocene isobutyl hydride complex, which upon exposure to H 2 affords the dimeric dihydride [ i Pr 2 Si(η 5 -3-SiMe 3 C 5 H 3 )(η 5 -3,4-(SiMe 3 ) 2 C 5 H 2 )ZrH 2 ] 2 . In a similar procedure the substituted indenyl complexes rac -(1-CMe 3 −C 9 H 6 )Zr(H)Cl and rac -(1-CMe 3 −C 9 H 6 )Zr(CH 2 CHMe 2 )(H) have been prepared. This synthetic methodology allows for the preparation of metallocene alkyl hydrides and dihydrides inaccessible by more traditional routes.