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Modulation of Proton-Coupled Electron Transfer through Molybdenum–Quinonoid Interactions

Henthorn, Justin T. and Agapie, Theodor (2016) Modulation of Proton-Coupled Electron Transfer through Molybdenum–Quinonoid Interactions. Inorganic Chemistry, 55 (11). pp. 5337-5342. ISSN 0020-1669.

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An expanded series of π-bound molybdenum–quinonoid complexes supported by pendant phosphines has been synthesized. These compounds formally span three protonation–oxidation states of the quinonoid fragment (catechol, semiquinone, quinone) and two different oxidation states of the metal (Mo^0, Mo^(II)), notably demonstrating a total of two protons and four electrons accessible in the system. Previously, the reduced Mo^0–catechol complex 1 and its reaction with dioxygen to yield the two-proton/two-electron oxidized Mo^0–quinone compound 4 was explored, while, herein, the expansion of the series to include the two-electron oxidized Mo^(II)–catechol complex 2, the one-proton/two-electron oxidized Mo–semiquinone complex 3, and the two-proton/four-electron oxidized MoII–quinone complexes 5 and 6 is reported. Transfer of multiple equivalents of protons and electrons from the Mo^0 and Mo^(II) catechol complexes, 1 and 2, to H atom acceptor TEMPO suggests the presence of weak O–H bonds. Although thermochemical analyses are hindered by the irreversibility of the electrochemistry of the present compounds, the reactivity observed suggests weaker O–H bonds compared to the free catechol, indicating that proton-coupled electron transfer can be facilitated significantly by the π-bound metal center.

Item Type:Article
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URLURL TypeDescription Information
Henthorn, Justin T.0000-0003-4876-2680
Agapie, Theodor0000-0002-9692-7614
Additional Information:© 2016 American Chemical Society. Received: February 8, 2016. Publication Date (Web): May 26, 2016. We thank Lawrence M. Henling and Dr. Michael Takase for crystallographic assistance and Choon Heng (Marcus) Low for synthesizing quinone 11 and for performing some of the control experiments. We thank Caltech and the NSF (CHE-1151918, T.A., and NSF GRFP, J.T.H.) for funding. T.A. is grateful for Sloan, Cottrell, and Dreyfus fellowships. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to Caltech, CHE-0639094. The authors declare no competing financial interest.
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Issue or Number:11
Record Number:CaltechAUTHORS:20160601-143209378
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Official Citation:Modulation of Proton-Coupled Electron Transfer through Molybdenum–Quinonoid Interactions Justin T. Henthorn and Theodor Agapie Inorganic Chemistry 2016 55 (11), 5337-5342 DOI: 10.1021/acs.inorgchem.6b00331
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67553
Deposited By: George Porter
Deposited On:01 Jun 2016 21:59
Last Modified:07 Apr 2020 16:19

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