Mechanism of the Electrocatalytic Reduction of Protons with Diaryldithiolene Cobalt Complexes

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• 作者：Christopher S. Letko ; Julien A. Panetier ; Martin Head-Gordon ; T. Don Tilley
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：July 2, 2014
• 年：2014
• 卷：136
• 期：26
• 页码：9364-9376
• 全文大小：579K
• ISSN：1520-5126

文摘

A series of dimeric cobalt-diaryldithiolene complexes [Co(S₂C₂Ar₂)₂]₂, possessing various aryl para substituents (OMe, F, Cl, and Br), were studied as electrocatalysts for proton reduction in nonaqueous media, in an effort to correlate dithiolene donor strength with catalyst activity. Cyclic voltammetry data acquired for the cobalt-diaryldithiolene dimers guided the isolation of chemically reduced monoanionic ([Co(S₂C₂Ar₂)₂]^{鈭?/sup>) and dianionic ([Co(S₂C₂Ar₂)₂]2鈥?/sup>) monomers. The potassium and tetrabutylammonium salts of dianionic cobalt-diaryldithiolene complexes have been characterized by single crystal X-ray crystallography. Treatment of the dianionic species with stoichiometric quantities of a weak acid afforded H₂ and the monoanionic cobalt-diaryldithiolene species. Density functional theory (BP86) suggests that hydrogen elimination proceeds through a diprotonated intermediate with a Co鈥揌 bond and a protonated S center. A transition state for transfer of the S鈥揌 proton to the metal center was located with a computed free energy of 5.9 kcal/mol, in solution (DMF via C-PCM approach).}