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

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journal contribution
posted on 2002-02-21, 00:00 authored by Jaime A. Pool, Christopher A. Bradley, Paul J. Chirik
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‘ ‘2Zr(H)Cl (Cp* = C5Me5, Cp‘ ‘ = 1,3-(SiMe3)2C5H3) were prepared in high yield. Further addition of tBuLi to Cp*Cp‘ ‘Zr(H)Cl affords the isobutyl hydride complex Cp*Cp‘ ‘Zr(CH2CHMe2)(H), which upon addition of 1 atm of dihydrogen undergoes rapid hydrogenolysis yielding the monomeric dihydride Cp*Cp‘ ‘ZrH2. In the absence of dihydrogen, the zirconocene dihydride undergoes reversible C−H activation of a cyclopentadienyl trimethylsilyl group, affording the “tuck-in” derivative Cp*(η5-1-SiMe3C5H3-3-(η1-SiMe2CH2))ZrH. Addition of 2 equiv of tBuLi to the ansa-zirconocene iPr2Si(η5-3-SiMe3C5H3)(η5-3,4-(SiMe3)2C5H2)ZrCl2 results in the corresponding zirconocene isobutyl hydride complex, which upon exposure to H2 affords the dimeric dihydride [iPr2Si(η5-3-SiMe3C5H3)(η5-3,4-(SiMe3)2C5H2)ZrH2]2. In a similar procedure the substituted indenyl complexes rac-(1-CMe3−C9H6)Zr(H)Cl and rac-(1-CMe3−C9H6)Zr(CH2CHMe2)(H) have been prepared. This synthetic methodology allows for the preparation of metallocene alkyl hydrides and dihydrides inaccessible by more traditional routes.