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Hydrogen Generation Catalyzed by Fluorinated Diglyoxime−Iron Complexes at Low Overpotentials

Rose, Michael J. and Gray, Harry B. and Winkler, Jay R. (2012) Hydrogen Generation Catalyzed by Fluorinated Diglyoxime−Iron Complexes at Low Overpotentials. Journal of the American Chemical Society, 134 (20). pp. 8310-8313. ISSN 0002-7863. http://resolver.caltech.edu/CaltechAUTHORS:20120621-073446298

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Abstract

Fe^(II) complexes containing the fluorinated ligand 1,2-bis(perfluorophenyl)ethane-1,2-dionedioxime (dAr^FgH_2; H = dissociable proton) exhibit relatively positive Fe^(II/I) reduction potentials. The air-stable difluoroborated species [(dAr^FgBF_2)_2Fe(py)_2] (2) electrocatalyzes H_2 generation at −0.9 V vs SCE with i_(cat)/i_p ≈ 4, corresponding to a turnover frequency (TOF) of ~ 20 s^(–1) [Faradaic yield (FY) = 82 ± 13%]. The corresponding monofluoroborated, proton-bridged complex [(dArFg2H-BF2)Fe(py)2] (3) exhibits an improved TOF of ~ 200 s^(–1) (i_(cat)/i_p ≈ 8; FY = 68 ± 14%) at −0.8 V with an overpotential of 300 mV. Simulations of the electrocatalytic cyclic voltammograms of 2 suggest rate-limiting protonation of an Fe“0” intermediate (k_(RLS) ≈ 200 M^(–1) s^(–1)) that undergoes hydride protonation to form H_2. Complex 3 likely reacts via protonation of an Fe^I intermediate that subsequently forms H_2 via a bimetallic mechanism (k_(RLS) ≈ 2000 M^(–1) s^(–1)). 3 catalyzes production at relatively positive potentials compared with other iron complexes.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ja300534rDOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja300534rPublisherArticle
ORCID:
AuthorORCID
Winkler, Jay R.0000-0002-4453-9716
Additional Information:© 2012 American Chemical Society. Received: January 17, 2012. Publication Date (Web): May 14, 2012. This work was supported by the NSF CCI Solar Fuels Program (CHE-0802907). M.J.R. was supported by an NSF ACC-F Fellowship (CHE-1042009). The Bruker APEXII diffractometer was obtained via an NSF CRIF:MU Award (CHE-0639094). We thank Larry Henling and Michael Day for solving the crystal structures.
Group:CCI Solar Fuels
Funders:
Funding AgencyGrant Number
NSFCHE-0802907
NSF Postdoctoral FellowshipCHE-1042009
NSFCHE-0639094
Record Number:CaltechAUTHORS:20120621-073446298
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120621-073446298
Official Citation:Hydrogen Generation Catalyzed by Fluorinated Diglyoxime–Iron Complexes at Low Overpotentials Michael J. Rose, Harry B. Gray, and Jay R. Winkler Journal of the American Chemical Society 2012 134 (20), 8310-8313
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31996
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:21 Jun 2012 14:57
Last Modified:16 Sep 2017 02:28

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