Computational Characterization of Redox Non-Innocence in Cobalt-Bis(Diaryldithiolene)-Catalyzed Proton Reduction

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• 作者：Julien A. Panetier ; Christopher S. Letko ; T. Don Tilley ; Martin Head-Gordon
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2016
• 出版时间：January 12, 2016
• 年：2016
• 卷：12
• 期：1
• 页码：223-230
• 全文大小：561K
• ISSN：1549-9626

文摘

Localized orbital bonding analysis (LOBA) was employed to probe the oxidation state in cobalt-bis(diaryldithiolene)-catalyzed proton reduction in nonaqueous media. LOBA calculations provide both the oxidation state and chemically intuitive views of bonding in cobalt-bis(diaryldithiolene) species and therefore allow characterization of the role of the redox non-innocent dithiolene ligand. LOBA results show that the reduction of the monoanion species [1Br]^? is metal-centered and gives a cobalt(II) ion species, [1Br]^2–, coordinated to two dianionic ene-1,2-dithiolates. This electronic configuration is in agreement with the solution magnetic moment observed for the analogous salt [1F]^2– (μ_eff = 2.39 μ_B). Protonation of [1Br]^2– yields the cobalt(III)-hydride [1Br(CoH)]^? species in which the Co–H bond is computed to be highly covalent (L?wdin populations close to 0.50 on cobalt and hydrogen atoms). Further reduction of [1Br(CoH)]^? forms a more basic cobalt(II)–H intermediate [1Br(CoH)]^2– (S = 0) from which protonation at sulfur gives a S–H bond syn to the Co–H bond. Formation of a cobalt-dihydrogen [1Br(CoH₂)]^? intermediate is calculated to occur via a homocoupling (H^? + H^? → H₂) step with a free energy of activation of 5.9 kcal/mol in solution (via C-PCM approach).