Regioselective protonation of ferrocene in superacid and formation of a CHFe bond. An experimental and theoretical study of the structure and dynamics of the ferrocenonium ion
作者:
Annika Karlsson,
Anders Broo,
Per Ahlberg,
期刊:
Canadian Journal of Chemistry
(NRC Available online 1999)
卷期:
Volume 77,
issue 5-6
页码: 628-633
ISSN:0008-4042
年代: 1999
DOI:10.1139/v99-053
出版商: NRC Research Press
数据来源: NRC
摘要:
Protonation of ferrocene has been suggested to take place on carbon (exo-protonation) or iron (endo-protonation). However, experiments have not been conclusive because of interfering exchange reactions. Now low-temperature protonation of ferrocene and [2H10]-ferrocene in superacid and direct observation of the carbocation by1H NMR at low temperature shows only primary protonation and that it exclusively takes place in anendo-fashion. Studies by DFT calculations using B3LYP hybrid functional indicate the presence of an intramolecular nonlinear CHFe bond and that the proton might be delocalized between carbon and iron. Potential energy barriers for degenerate rearrangements of the hydride bridged carbocation are low, suggesting that the proton might be delocalized between all 10 carbons and iron. The NMR results are consistent with such an interpretation.Key words: regioselective, protonation, superacid, ferrocenonium io
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