π-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysis

Handle URI:
http://hdl.handle.net/10754/562188
Title:
π-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysis
Authors:
Credendino, Raffaele; Falivene, Laura; Cavallo, Luigi ( 0000-0002-1398-338X )
Abstract:
In this work, we calculate the redox potential in a series of Ir and Ru complexes bearing a N-heterocyclic carbene (NHC) ligand presenting different Y groups in the para position of the aromatic N-substituent. The calculated redox potentials excellently correlate with the experimental ΔE 1/2 potentials, offering a handle to rationalize the experimental findings. Analysis of the HOMO of the complexes before oxidation suggests that electron-donating Y groups destabilize the metal centered HOMO. Energy decomposition of the metal-NHC interaction indicates that electron-donating Y groups reinforce this interaction in the oxidized complexes. Analysis of the electron density in the reduced and oxidized states of representative complexes indicates a clear donation from the C ipso of the N-substituents to an empty d orbital on the metal. In case of the Ru complexes, this mechanism involves the Ru-alkylidene moiety. All of these results suggest that electron-donating Y groups render the aromatic N-substituent able to donate more density to electron-deficient metals through the C ipso atom. This conclusion suggests that electron-donating Y groups could stabilize higher oxidation states during catalysis. To test this hypothesis, we investigated the effect of differently donating Y groups in model reactions of Ru-catalyzed olefin metathesis and Pd-catalyzed C-C cross-coupling. Consistent with the experimental results, calculations indicate an easier reaction pathway if the N-substituent of the NHC ligand presents an electron-donating Y group. © 2012 American Chemical Society.
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division; KAUST Catalysis Center (KCC); Physical Sciences and Engineering (PSE) Division; Chemical Science Program
Publisher:
American Chemical Society (ACS)
Journal:
Journal of the American Chemical Society
Issue Date:
16-May-2012
DOI:
10.1021/ja212133j
Type:
Article
ISSN:
00027863
Sponsors:
This project has been supported by the European Community (FP7 project CP-FP 211468-2 EUMET).
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; Chemical Science Program; KAUST Catalysis Center (KCC); Biological and Environmental Sciences and Engineering (BESE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorCredendino, Raffaeleen
dc.contributor.authorFalivene, Lauraen
dc.contributor.authorCavallo, Luigien
dc.date.accessioned2015-08-03T09:46:50Zen
dc.date.available2015-08-03T09:46:50Zen
dc.date.issued2012-05-16en
dc.identifier.issn00027863en
dc.identifier.doi10.1021/ja212133jen
dc.identifier.urihttp://hdl.handle.net/10754/562188en
dc.description.abstractIn this work, we calculate the redox potential in a series of Ir and Ru complexes bearing a N-heterocyclic carbene (NHC) ligand presenting different Y groups in the para position of the aromatic N-substituent. The calculated redox potentials excellently correlate with the experimental ΔE 1/2 potentials, offering a handle to rationalize the experimental findings. Analysis of the HOMO of the complexes before oxidation suggests that electron-donating Y groups destabilize the metal centered HOMO. Energy decomposition of the metal-NHC interaction indicates that electron-donating Y groups reinforce this interaction in the oxidized complexes. Analysis of the electron density in the reduced and oxidized states of representative complexes indicates a clear donation from the C ipso of the N-substituents to an empty d orbital on the metal. In case of the Ru complexes, this mechanism involves the Ru-alkylidene moiety. All of these results suggest that electron-donating Y groups render the aromatic N-substituent able to donate more density to electron-deficient metals through the C ipso atom. This conclusion suggests that electron-donating Y groups could stabilize higher oxidation states during catalysis. To test this hypothesis, we investigated the effect of differently donating Y groups in model reactions of Ru-catalyzed olefin metathesis and Pd-catalyzed C-C cross-coupling. Consistent with the experimental results, calculations indicate an easier reaction pathway if the N-substituent of the NHC ligand presents an electron-donating Y group. © 2012 American Chemical Society.en
dc.description.sponsorshipThis project has been supported by the European Community (FP7 project CP-FP 211468-2 EUMET).en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleπ-face donation from the aromatic N-substituent of N-heterocyclic carbene ligands to metal and its role in catalysisen
dc.typeArticleen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentChemical Science Programen
dc.identifier.journalJournal of the American Chemical Societyen
dc.contributor.institutionDipartimento di Chimica e Biologia, Università di Salerno, Via Ponte don Melillo, I-84084 Fisciano (SA), Italyen
kaust.authorCredendino, Raffaeleen
kaust.authorCavallo, Luigien
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