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Snapshots of a Migrating H-Atom: Characterization of a Reactive Iron(III) Indenide Hydride and its Nearly Isoenergetic Ring-Protonated Iron(I) Isomer

Drover, Marcus W. and Schild, Dirk J. and Oyala, Paul H. and Peters, Jonas C. (2019) Snapshots of a Migrating H-Atom: Characterization of a Reactive Iron(III) Indenide Hydride and its Nearly Isoenergetic Ring-Protonated Iron(I) Isomer. Angewandte Chemie International Edition, 58 (43). pp. 15504-15511. ISSN 1433-7851. doi:10.1002/anie.201909050.

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We report the characterization of an S=1/2 iron π‐complex, [Fe(η⁶‐IndH)(depe)]⁺ (Ind=Indenide (C₉H₇⁻), depe=1,2‐bis(diethylphosphino)ethane), which results via C−H elimination from a transient Fe^(III) hydride, [Fe(η³:η²‐Ind)(depe)H]⁺. Owing to weak M−H/C−H bonds, these species appear to undergo proton‐coupled electron transfer (PCET) to release H₂ through bimolecular recombination. Mechanistic information, gained from stoichiometric as well as computational studies, reveal the open‐shell π‐arene complex to have a BDFE_(C‐H) value of ≈50 kcal mol⁻¹, roughly equal to the BDFE_(Fe‐H) of its Fe^(III)−H precursor (ΔG°≈0 between them). Markedly, this reactivity differs from related Fe(η⁵‐Cp/Cp*) compounds, for which terminal Fe^(III)−H cations are isolable and have been structurally characterized, highlighting the effect of a benzannulated ring (indene). Overall, this study provides a structural, thermochemical, and mechanistic foundation for the characterization of indenide/indene PCET precursors and outlines a valuable approach for the differentiation of a ring‐ versus a metal‐bound H‐atom by way of continuous‐wave (CW) and pulse EPR (HYSCORE) spectroscopic measurements.

Item Type:Article
Related URLs:
URLURL TypeDescription
Drover, Marcus W.0000-0002-2186-1040
Oyala, Paul H.0000-0002-8761-4667
Peters, Jonas C.0000-0002-6610-4414
Additional Information:© 2019 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim. Issue Online: 14 October 2019; Version of Record online: 18 September 2019; Accepted manuscript online: 29 August 2019; Manuscript received: 22 July 2019. The authors are grateful to the Department of Energy for support via Grant No. DOE‐0235032. The Caltech EPR facility was supported by the National Science Foundation via grant No. NSF MRI‐153194, as well as the Dow Next Generation Educator Fund. The Beckman Institute is thanked for X‐ray support. M.W.D. acknowledges NSERC (Banting PDF award), and M.W.D./D.J.S thank the Resnick Sustainability Institute at Caltech for fellowships. The authors declare no conflict of interest.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DOE-0235032
Dow Next Generation Educator FundUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:HYSCORE; metalloradicals; PCET reactivity; pulse EPR; weak C−H bonds
Issue or Number:43
Record Number:CaltechAUTHORS:20191203-101325731
Persistent URL:
Official Citation:M. W. Drover, D. J. Schild, P. H. Oyala, J. C. Peters, Angew. Chem. Int. Ed. 2019, 58, 15504.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100162
Deposited By: Tony Diaz
Deposited On:03 Dec 2019 18:59
Last Modified:16 Nov 2021 17:52

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