Solvent promoted reversible cyclometalation in a tethered NHC iridium complex

Wheatley, James E.; Ohlin, C. André; Chaplin, Adrian B.

doi:10.1039/c3cc48015a

Cited by 22 publications

(7 citation statements)

References 32 publications

(5 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With a view toward exploring the organometallic chemistry of low-coordinate NHC complexes of rhodium and iridium, some of us have recently begun to expand the coordination chemistry of Glorius’ bioxazoline-based variants (IBiox), seeking to exploit the conformationally rigid nature of these ligands to avoid intramolecular cyclometalation reactions that can occur via C–H bond activation of the downward-pointing alkyl and aryl NHC appendages . In particular, we have focused our initial efforts on studying the coordination chemistry of IBioxMe 4 , which shares many structural similarities with the commonly employed I t Bu ligand, an NHC that has been shown to undergo cyclometalation reactions when partnered with reactive late-transition-metal fragments (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe₄ Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

et al. 2015

Self Cite

View full text Add to dashboard Cite

. (2015) Rhodium(I) and Iridium(I) complexes of the conformationally rigid IBioxMe4Ligand : computational and experimental studies of unusually tilted NHC coordination geometries. Organometallics, 34 (20). pp. 5099-5112. Permanent WRAP URL:http://wrap.warwick.ac.uk/76666 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organometallics copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work http://pubs.acs.org/page/policy/articlesonrequest/index.html ." A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL above for details on accessing the published version and note that access may require a subscription.

show abstract

Section: Introductionmentioning

confidence: 99%

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe₄ Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, transferring the synthesis protocol of the Rh complex to the iridium case led to formation of the cod-isomerized complex bearing a κ 1 ,η 3 -coordinating C 8 H 12 -ligand, as shown below. Therefore, we decided to investigate the cod-isomerization in more detail in order to shed light onto the partly contradictory conditions given in the literature. − ,, …”

mentioning

confidence: 99%

Identifying and Rationalizing the Conditions for the Isomerization of 1,5-Cyclooctadiene in Iridium Complexes by Experimental and Theoretical Mechanistic Studies

2015

View full text Add to dashboard Cite

The independent synthesis of the biscarbene complexes [Ir(cod)(vegi R )]PF 6 (2) (cod =1,5-cyclooctadiene, vegi R = bidentate N-heterocyclic carbene) as well as their isomerized complexes [Ir(1-κ-4,5,6-η-C 8 H 12 )(NCCH 3 )(vegi R )]-PF 6 (3) is described. We elucidated acetic acid as the catalyst and coordinated acetonitrile as the thermodynamic driving force for this cod-isomerization. By using the stronger trifluoroacetic acid, we isolated complex [Ir(cod)(F 3 CCO 2 )(H)(vegi nPr )]PF 6 (7a) as an intermediate of the isomerization. From H/D exchange experiments as well as DFT calculations, we conclude that after formation of the Ir−H complex, an olefin insertion, followed by a concerted metalation-deprotonation step and a coordination of acetonitrile, is the mechanistic pathway. On the basis of our findings, we were able to carry out the cod-isomerization for the first time also for the less-electron-rich complex [Ir(2,2′-bipy)(cod)]PF 6 (8) (2,2-bipy = 2,2′-bipyridine).

show abstract

“…Another possible deactivation pathway involves the activation of C–H or even C–C bonds in the N-side chain of the NHC. − This process, however, does not always result in decomposition as such metallacycles can be synthesized in good yield and characterized using conventional methods. − In some cases they can even play an active role in catalysis. , Most of the related works, however, were done on ruthenium complexes. Only a few examples with other metals exhibiting such behavior were found and they can be described almost exclusively with the general formula Cp*Ir(NHC). ,, …”

Section: Introductionmentioning

confidence: 99%

“…Only a few examples with other metals exhibiting such behavior were found and they can be described almost exclusively with the general formula Cp*Ir(NHC). 30,37,38 Based on these considerations, we aim to investigate the possible role of the C−H activation process in a water-soluble iridium based carbene-phosphine complex, Na 2 [Ir(emim)(η 4 -COD)(mtppts)] (COD = 1,5-cyclooctadiene, emim = 1-ethyl-3-methylimidazol-2-ylidene, mtppts = trisulfonated triphenylphosphine) developed in our research group. 39 This catalyst offers exceptionally good performance in the formatebicarbonate system of hydrogen storage.…”

Section: ■ Introductionmentioning

confidence: 99%

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

Fehér

Horváth²,

Joó

et al. 2018

Inorg. Chem.

View full text Add to dashboard Cite

A novel iridium based, water-soluble phosphine-NHC (N-heterocyclic carbene) complex, Na[Ir( emim)(η-COD)( mtppts)] was previously developed in our research group. It was shown that it is a very effective catalyst for the reversible storage of hydrogen based on the formate-bicarbonate equilibrium. In this paper, we present a DFT investigation on the noninnocent behavior of the NHC ligand toward C-H activation of the N-ethyl side chain and its possible role in the hydrogen storage mechanism. After preliminary investigations, using both computations and NMR measurements, we conclude that the COD ligand leaves the precatalyst irreversibly and the C-H activation takes place on a monophosphine complex. Two main pathways are considered in which the active Ir(III) complexes are generated differently: One is the cyclometalation path involving the ethyl side chain, the other is the oxidative addition step of a water molecule which has a higher barrier but provide a more stable starting state. We find that though the latter, a catalytic cycle where a hydride is abstracted from formate and gets protonated by solvent molecules gives the lowest calculated energy barrier, +25.8 kcal mol. That is, avoiding further redox processes is preferred. There are other pathways involving thermodynamically accessible C-H activated iridacycles but those involve slightly higher overall activation barriers due to the required Ir(I)/Ir(III) transitions. The cycle which involves only iridacycle intermediates offer the lowest energy span (energy difference calculated between only the highest and lowest energy points inside the cycle), however. Together with the experimental results, this implies that C-H activation of the N-ethyl side chain happens off-cycle or the starting solvent addition step of the dominant pathway is blocked kinetically. We also discuss the hydrogen uptake reaction catalyzed by cyclometalated species where the reduction of CO is preferred over reversing the first main cycle.

show abstract

Solvent promoted reversible cyclometalation in a tethered NHC iridium complex

Cited by 22 publications

References 32 publications

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe₄ Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe₄ Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

Identifying and Rationalizing the Conditions for the Isomerization of 1,5-Cyclooctadiene in Iridium Complexes by Experimental and Theoretical Mechanistic Studies

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

Contact Info

Product

Resources

About

Solvent promoted reversible cyclometalation in a tethered NHC iridium complex

Cited by 22 publications

References 32 publications

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe4 Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe4 Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

Identifying and Rationalizing the Conditions for the Isomerization of 1,5-Cyclooctadiene in Iridium Complexes by Experimental and Theoretical Mechanistic Studies

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

Contact Info

Product

Resources

About

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe₄ Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries

Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe₄ Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries