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Combination of Redox-Active Ligand and Lewis Acid for Dioxygen Reduction with π-Bound Molybdenum−Quinonoid Complexes

Henthorn, Justin T. and Lin, Sibo and Agapie, Theodor (2015) Combination of Redox-Active Ligand and Lewis Acid for Dioxygen Reduction with π-Bound Molybdenum−Quinonoid Complexes. Journal of the American Chemical Society, 137 (4). pp. 1458-1464. ISSN 0002-7863.

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A series of π-bound Mo−quinonoid complexes supported by pendant phosphines have been synthesized. Structural characterization revealed strong metal–arene interactions between Mo and the π system of the quinonoid fragment. The Mo–catechol complex (2a) was found to react within minutes with 0.5 equiv of O_2 to yield a Mo–quinone complex (3), H_2O, and CO. Si- and B-protected Mo–catecholate complexes also react with O_2 to yield 3 along with (R_2SiO)_n and (ArBO)_3 byproducts, respectively. Formally, the Mo–catecholate fragment provides two electrons, while the elements bound to the catecholate moiety act as acceptors for the O_2 oxygens. Unreactive by itself, the Mo–dimethyl catecholate analogue reduces O_2 in the presence of added Lewis acid, B(C_6F_5)_3, to generate a MoI species and a bis(borane)-supported peroxide dianion, [[(F_5C_6)_3B]_2O_2^(2–)], demonstrating single-electron-transfer chemistry from Mo to the O_2 moiety. The intramolecular combination of a molybdenum center, redox-active ligand, and Lewis acid reduces O_2 with pendant acids weaker than B(C_6F_5)_3. Overall, the π-bound catecholate moiety acts as a two-electron donor. A mechanism is proposed in which O_2 is reduced through an initial one-electron transfer, coupled with transfer of the Lewis acidic moiety bound to the quinonoid oxygen atoms to the reduced O_2 species.

Item Type:Article
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URLURL TypeDescription Information
Henthorn, Justin T.0000-0003-4876-2680
Lin, Sibo0000-0001-5922-6694
Agapie, Theodor0000-0002-9692-7614
Additional Information:© 2015 American Chemical Society. Received: September 29, 2014; Revised: December 4, 2014; Published: January 10, 2015. We thank Lawrence M. Henling and Dr. Michael Takase for crystallographic assistance, Prof. John E. Bercaw for providing access to a Toepler pump in his laboratory, and Christine Cheng for assistance in organic synthesis. We are grateful to Caltech and the NSF (CHE-1151918 to T.A.; GRFP to J.T.H.) for funding. T.A. is a Sloan, Cottrell, and Dreyfus Fellow. The APEX II X-ray diffractometer was purchased via an NSF CRIF:MU Award to Caltech (CHE-0639094).
Funding AgencyGrant Number
NSF Graduate Research Fellowship ProgramUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20150316-110108648
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Official Citation:Combination of Redox-Active Ligand and Lewis Acid for Dioxygen Reduction with π-Bound Molybdenum−Quinonoid Complexes Justin T. Henthorn, Sibo Lin, and Theodor Agapie Journal of the American Chemical Society 2015 137 (4), 1458-1464 DOI: 10.1021/ja5100405
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55785
Deposited By: Tony Diaz
Deposited On:16 Mar 2015 19:38
Last Modified:07 Apr 2020 16:22

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