Ueng, SH and Solovyev, A and Yuan, X and Geib, SJ and Fensterbank, L and Lacôte, E and Malacria, M and Newcomb, M and Walton, JC and Curran, DP
(2009)
N-heterocyclic carbene boryl radicals: A new class of boron-centered radical.
Journal of the American Chemical Society, 131 (31).
11256 - 11262.
ISSN 0002-7863
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Abstract
Reduction of xanthates by N-heterocyclic carbene boranes (NHC-boranes) has been suggested to occur by a radical chain mechanism involving heretofore unknown NHC-boryl radicals. In support of this suggestion, both the expected borane dithiocarbonate product and an unexpected borane xanthate product have now been isolated. These are the first NHC-boranes with boron-sulfur bonds, and their structures have been secured by spectroscopic and crystallographic means. The first rate constants for H-atom transfer from an NHC borane complex were determined by using the ring opening of a substituted cyclobutylcarbinyl radical as a clock reaction. The rate constant for reaction of the NHC-borane with a secondary alkyl radical at ambient temperature is 4 × 104 M-1 s-1, and the Arrhenius function displayed an entropic term (log A term) that was typical for a bimolecular reaction. The B-H bond dissociation energy of an NHC-borane complex has been estimated at 88 kcal/mol. The putative NHC-boryl radical in these transformations has been detected by EPR spectroscopy. Spectral analysis suggests that it is a π-radical, analogous to the benzyl radical. © 2009 American Chemical Society.
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Item Type: |
Article
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Status: |
Published |
Creators/Authors: |
Creators | Email | Pitt Username | ORCID ![](/images/orcid_id_24x24.png) |
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Ueng, SH | | | | Solovyev, A | | | | Yuan, X | | | | Geib, SJ | geib@pitt.edu | GEIB | 0000-0002-9160-7857 | Fensterbank, L | | | | Lacôte, E | | | | Malacria, M | | | | Newcomb, M | | | | Walton, JC | | | | Curran, DP | curran@pitt.edu | CURRAN | |
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Date: |
12 August 2009 |
Date Type: |
Publication |
Journal or Publication Title: |
Journal of the American Chemical Society |
Volume: |
131 |
Number: |
31 |
Page Range: |
11256 - 11262 |
DOI or Unique Handle: |
10.1021/ja904103x |
Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
Refereed: |
Yes |
ISSN: |
0002-7863 |
PubMed ID: |
19606860 |
Date Deposited: |
21 Feb 2013 22:53 |
Last Modified: |
13 Jun 2021 01:55 |
URI: |
http://d-scholarship-dev.library.pitt.edu/id/eprint/17350 |
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