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Snapshots of a Migrating H-atom: Characterization of a Reactive Fe(III) Indenide Hydride and its Nearly Isoenergetic Ring-Protonated Fe(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 Fe(III) Indenide Hydride and its Nearly Isoenergetic Ring-Protonated Fe(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 = ½ iron π‐complex, [Fe(η^6‐IndH)(depe)]^+ (Ind = Indenide (C_9H_(7^‐_), depe = 1,2‐bis(diethylphosphino)ethane), which results via C‐H elimination from a transient Fe^(III) hydride, [Fe(η^3:η^2‐Ind)(depe)H]^+. Owing to weak M‐H/C‐H bonds, these species undergo proton‐coupled electron transfer (PCET) to release H_2 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^o ≈ 0 between them). Markedly, this reactivity differs from related Fe(η^5‐Cp/Cp^*) compounds, for which terminal Fe^(III)‐H cations are isolable and have been structurally characterized, highlighting the effect of a benzannulated (indene) ring. Overall, this study provides a structural, thermochemical, and mechanistic foundation for the characterization of indenide/indene PCET precursors and out‐lines 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
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URLURL TypeDescription Information
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. Manuscript received: July 22, 2019; Accepted manuscript online: August 29, 2019; Version of record online: September 18, 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 to MWD), and M.W.D./D.J.S. thank the Resnick Sustainability Institute at Caltech for fellowships. The authors declare no competing financial interest.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DOE-0235032
Dow Next Generation Educator FundUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:electronic structure; iron; metalloradicals; Structure elucidation; alkene ligands
Issue or Number:43
Record Number:CaltechAUTHORS:20190829-111225922
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:98338
Deposited By: George Porter
Deposited On:30 Aug 2019 14:47
Last Modified:16 Nov 2021 17:38

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