Activation of an alkyl C-H bond geminal to an agostic interaction: An unusual mode of base-induced C-H activation

L Jonas L Haeller, Michael J. Page, Stuart A. Macgregor, Mary F. Mahon, Michael K. Whittlesey

Research output: Contribution to journalArticle

Abstract

Deuterium labeling studies indicate that base-induced intramolecular C-H activation in the agostic complex 2-D proceeds with exclusive removal of a proton from the methyl arm of an iPr substituent on the N-heterocyclic carbene (NHC) ligand. Computational studies show that this alkyl C-H bond activation reaction involves deprotonation of one of the C-H bonds that is geminal to the agostic interaction, rather than the agostic C-H bond itself. The reaction is readily accessible at room temperature, and a computed activation barrier of ?E†calcd = +11.8 kcal/mol is found when the NHC 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene is employed as the external base. Charge analysis reveals that the geminal hydrogens are in fact more acidic than the agostic proton, consistent with their more facile deprotonation. © 2009 American Chemical Society.

Original languageEnglish
Pages (from-to)4604-4605
Number of pages2
JournalJournal of the American Chemical Society
Volume131
Issue number13
DOIs
Publication statusPublished - 8 Apr 2009

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Deprotonation
Chemical activation
Protons
Deuterium
Labeling
Hydrogen
Ligands
Temperature
carbene

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Haeller, L Jonas L ; Page, Michael J. ; Macgregor, Stuart A. ; Mahon, Mary F. ; Whittlesey, Michael K. / Activation of an alkyl C-H bond geminal to an agostic interaction : An unusual mode of base-induced C-H activation. In: Journal of the American Chemical Society. 2009 ; Vol. 131, No. 13. pp. 4604-4605.
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abstract = "Deuterium labeling studies indicate that base-induced intramolecular C-H activation in the agostic complex 2-D proceeds with exclusive removal of a proton from the methyl arm of an iPr substituent on the N-heterocyclic carbene (NHC) ligand. Computational studies show that this alkyl C-H bond activation reaction involves deprotonation of one of the C-H bonds that is geminal to the agostic interaction, rather than the agostic C-H bond itself. The reaction is readily accessible at room temperature, and a computed activation barrier of ?E†calcd = +11.8 kcal/mol is found when the NHC 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene is employed as the external base. Charge analysis reveals that the geminal hydrogens are in fact more acidic than the agostic proton, consistent with their more facile deprotonation. {\circledC} 2009 American Chemical Society.",
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Activation of an alkyl C-H bond geminal to an agostic interaction : An unusual mode of base-induced C-H activation. / Haeller, L Jonas L; Page, Michael J.; Macgregor, Stuart A.; Mahon, Mary F.; Whittlesey, Michael K.

In: Journal of the American Chemical Society, Vol. 131, No. 13, 08.04.2009, p. 4604-4605.

Research output: Contribution to journalArticle

TY - JOUR

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AU - Haeller, L Jonas L

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AB - Deuterium labeling studies indicate that base-induced intramolecular C-H activation in the agostic complex 2-D proceeds with exclusive removal of a proton from the methyl arm of an iPr substituent on the N-heterocyclic carbene (NHC) ligand. Computational studies show that this alkyl C-H bond activation reaction involves deprotonation of one of the C-H bonds that is geminal to the agostic interaction, rather than the agostic C-H bond itself. The reaction is readily accessible at room temperature, and a computed activation barrier of ?E†calcd = +11.8 kcal/mol is found when the NHC 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene is employed as the external base. Charge analysis reveals that the geminal hydrogens are in fact more acidic than the agostic proton, consistent with their more facile deprotonation. © 2009 American Chemical Society.

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