Rotational versus Migration Isomerism in [{(tBuC5H4)2NbH(3-Te)(
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- 作者：Martin Brandl ; Henri Brunner ; Joachim Wachter ; and Manfred Zabel
- 刊名：Organometallics
- 出版年：2002
- 出版时间：July 8, 2002
- 年：2002
- 卷：21
- 期：14
- 页码：3069 - 3072
- 全文大小：70K
- 年卷期：v.21,no.14(July 8, 2002)
- ISSN：1520-6041
文摘
The reaction of [Cp'2Nb(Te2)H] (1) (Cp' =tBuC5H4) with [Fe2(CO)9] gives [{Cp'2NbH(Te)2}Fe2(CO)6] (2). Compound 2 reacts with [Cr(CO)5THF] to give[{Cp'2NbH(Te)2Fe2(CO)6}·Cr(CO)5] (3) in nearly quantitative yield. The crystal structure of 3 reveals that theFe2(CO)6 unit in this complex (and consequently in 2) isinserted in a perpendicular manner into the originalNbTe2 moiety of 1, while the incoming Cr(CO)5 fragmentis attached at the central Te atom and in vicinity (vic)to the Nb-H moiety. 1H NMR investigations of solutionsof 3 at -80 
C show that only the sterically crowded vic-3has been separated by recrystallization. At -60 C arapid exchange is observed for the ring protons, whichmay be explained by rotation of the Cp' rings aroundthe Cp'-Nb axes. Above 0 C an additional set of C5H4,tBu, and NbH resonances appears, which may be assigned to migration of the Cr(CO)5 fragment from thecentral to the lateral Te atom. The resulting opp-3 is ina 55:45 equilibrium with vic-3 at 20 C.
C show that only the sterically crowded vic-3has been separated by recrystallization. At -60 C arapid exchange is observed for the ring protons, whichmay be explained by rotation of the Cp' rings aroundthe Cp'-Nb axes. Above 0 C an additional set of C5H4,tBu, and NbH resonances appears, which may be assigned to migration of the Cr(CO)5 fragment from thecentral to the lateral Te atom. The resulting opp-3 is ina 55:45 equilibrium with vic-3 at 20 C.