Novel Rearrangement Reactions. 1. Molecular Rearrangement via Metathesis between Intramolecular Si-Si and Fe-Fe Bonds
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- 作者：Xiuzhong Zhou ; Yongqiang Zhang ; Wenhua Xie ; Shansheng Xu ; and Jie Sun
- 刊名：Organometallics
- 出版年：1997
- 出版时间：July 22, 1997
- 年：1997
- 卷：16
- 期：15
- 页码：3474 - 3481
- 全文大小：429K
- 年卷期：v.16,no.15(July 22, 1997)
- ISSN：1520-6041
文摘
Thermal treatment oft-BuC5H4Me2SiSiMe2C5H4-t-Buwith Fe(CO)5 in xylene gave thediiron complex(Me2SiSiMe2)[(
5-t-BuC5H3)Fe(CO)]2(
-CO)2(3), existing as a mixture of cisand trans isomers (3c and 3t) which wereseparated by preparative TLC. When the twoisomers were heated respectively in xylene, the cis substrate(3c) rearranged to the transproduct[Me2Si(5-t-BuC5H3)Fe(CO)2]2(4t), while the trans substrate (3t) afforded thecisproduct[Me2Si(5-t-BuC5H3)Fe(CO)2]2(4c). This indicates that the rearrangementreactionis stereospecific. Complexes[(5:5-C5H4Me2SiSiMe2C5R3R')Fe(CO)]2(-CO)2(R = H, R' =t-Bu, 5; R = R' = Me, 6),containing different cyclopentadienyl groups, werepreparedsimilarly. Their respective rearrangement reactions only yieldedthe corresponding unsymmetrical products[(Me2Si)(5-C5H4)Fe(CO)2][(Me2Si)(5-C5R3R')Fe(CO)2](R = H, R' = t-Bu,7; R = R' = Me, 8); no symmetricaldisproportionation products were detected. Thisindicatesthat the reaction proceeds via an intramolecular rather thanintermolecular pathway. Theconclusion is further confirmed by the fact that no crossover productwas formed insubsequent rearrangement between two different substrates. Probingthe reaction by ESRspectroscopy shows that the reaction proceeds via an intermediatecontaining iron-centeredradicals. On the basis of these experimental facts, an alternativemechanism for therearrangement reaction is proposed. Molecular structures of3c, 3t, 4t, and 4cweredetermined by X-ray diffraction.
5-t-BuC5H3)Fe(CO)]2(-CO)2(3), existing as a mixture of cisand trans isomers (3c and 3t) which wereseparated by preparative TLC. When the twoisomers were heated respectively in xylene, the cis substrate(3c) rearranged to the transproduct[Me2Si(5-t-BuC5H3)Fe(CO)2]2(4t), while the trans substrate (3t) afforded thecisproduct[Me2Si(5-t-BuC5H3)Fe(CO)2]2(4c). This indicates that the rearrangementreactionis stereospecific. Complexes[(5:5-C5H4Me2SiSiMe2C5R3R')Fe(CO)]2(-CO)2(R = H, R' =t-Bu, 5; R = R' = Me, 6),containing different cyclopentadienyl groups, werepreparedsimilarly. Their respective rearrangement reactions only yieldedthe corresponding unsymmetrical products[(Me2Si)(5-C5H4)Fe(CO)2][(Me2Si)(5-C5R3R')Fe(CO)2](R = H, R' = t-Bu,7; R = R' = Me, 8); no symmetricaldisproportionation products were detected. Thisindicatesthat the reaction proceeds via an intramolecular rather thanintermolecular pathway. Theconclusion is further confirmed by the fact that no crossover productwas formed insubsequent rearrangement between two different substrates. Probingthe reaction by ESRspectroscopy shows that the reaction proceeds via an intermediatecontaining iron-centeredradicals. On the basis of these experimental facts, an alternativemechanism for therearrangement reaction is proposed. Molecular structures of3c, 3t, 4t, and 4cweredetermined by X-ray diffraction.