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A Ru(I) Metalloradical That Catalyzes Nitrene Coupling to Azoarenes from Arylazides

Takaoka, Ayumi and Moret, Marc-Etienne and Peters, Jonas C. (2012) A Ru(I) Metalloradical That Catalyzes Nitrene Coupling to Azoarenes from Arylazides. Journal of the American Chemical Society, 134 (15). pp. 6695-6706. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20120514-132407274

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Abstract

Unusual N–N coupling of aryl azides to yield azoarenes is demonstrated by the Ru(I) metalloradical, [SiP^(iPr)_3]Ru(N_2) (4) ([SiP^(iPr)_3] = (2-iPr_(2)PC_(6)H_(4))_(3)Si^–). The yield of the azoarene is dependent on the substituent on the aryl azide, and the reaction is catalytic for p-methoxy and p-ethoxy phenyl azides, while no azoarene is observed for p-trifluoromethylphenyl azide. Studies aimed at probing the viability of a bimolecular coupling mechanism of metal imide species, as shown in the related [SiP^(iPr)_3]Fe system, have led to the isolation of several structurally unusual complexes including the ruthenium(IV) imide, 7-OMe, as well as the Ru(II) azide adduct 8-OMe. One electron reduction of 7-OMe complex led to the isolation of the formally Ru(III) imide complex, [SiP^(iPr)_3]Ru(NAr) (Ar = p-MeOC_(6)H_(4), 5-OMe). EPR spectroscopy on 5-OMe suggests that the complex is electronically similar to the previously reported imide complex, [SiP^(iPr)_3]Ru(NAr) (Ar = p-CF_(3)C_(6)H_(4),5-CF_(3)), and features radical character on the NAr moiety, but to a greater degree. The stability of 5-OMe establishes that bimolecular coupling of 5-OMe is kinetically inconsistent with the reaction. Further studies rule out mechanisms in which 5-OMe reacts directly with free aryl azide or a transient Ru(I) azide adduct. Together, these studies show that 5-OMe is likely uninvolved in the catalytic cycle and demonstrates the influence of the metal center on the mechanism of reaction. Instead, we favor a mechanism in which free aryl nitrene is released during the catalytic cycle and combines with itself or with free aryl azide to yield the azoarene.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ja211603fDOIUNSPECIFIED
http://pubs.acs.org/doi/abs/10.1021/ja211603fPublisherUNSPECIFIED
ORCID:
AuthorORCID
Peters, Jonas C.0000-0002-6610-4414
Additional Information:© 2012 American Chemical Society. Received: December 12, 2011; Published: March 1, 2012. We acknowledge the generosity of NSF (Grant CHE-0750234) and the Gordon and Betty Moore Foundation for support of this work. M.-E.M. acknowledges a Fellowship for Advanced Researchers from the Swiss National Science Foundation. We also thank Dr. Hill Harman for insightful discussions. Dr. Peter Müller, Larry Henling, and Charlene Tsay provided crystallographic assistance.
Funders:
Funding AgencyGrant Number
NSFCHE-0750234
Gordon and Betty Moore FoundationUNSPECIFIED
Swiss National Science Foundation Fellowship for Advanced ResearchersUNSPECIFIED
Issue or Number:15
Record Number:CaltechAUTHORS:20120514-132407274
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20120514-132407274
Official Citation:A Ru(I) Metalloradical That Catalyzes Nitrene Coupling to Azoarenes from Arylazides Ayumi Takaoka, Marc-Etienne Moret, and Jonas C. Peters Journal of the American Chemical Society 2012 134 (15), 6695-6706
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31456
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:15 May 2012 16:18
Last Modified:26 Nov 2019 11:15

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