Trifluoromethylation of a well-defined square-planar Aryl-NiII complex involving NiIII/CF3 and NiIV−CF3 intermediate species

ROVIRA, Mireia, ROLDÁN-GÓMEZ, Steven, MARTIN-DIACONESCU, Vlad, WHITEOAK, Christopher, COMPANY, Anna, LUIS, Josep and RIBAS, Xavi (2017). Trifluoromethylation of a well-defined square-planar Aryl-NiII complex involving NiIII/CF3 and NiIV−CF3 intermediate species. Chemistry - A European Journal, 23 (48), 11662-11668.

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Ni-mediated trifluoromethylation of an aryl−Br bond in model macrocyclic ligands (Ln−Br) has been thoroughly studied, starting with an oxidative addition at Ni0 to obtain well-defined aryl-NiII-Br complexes ([Ln−NiII]Br). Abstraction of the halide with AgX (X=OTf− or ClO4−) thereafter provides [Ln−NiII](OTf). The nitrate analogue has been obtained through a direct C−H activation of an aryl−H bond using NiII salts, and this route has been studied by X-ray absorption spectroscopy (XAS). Crystallographic XRD and XAS characterization has shown a tight macrocyclic coordination in the aryl−NiII complex, which may hamper direct reaction with nucleophiles. On the contrary, enhanced reactivity is observed with oxidants, and the reaction of [Ln−NiII](OTf) with CF3+ sources afforded Ln−CF3 products in quantitative yield. A combined experimental and theoretical mechanistic study provides new insights into the operative mechanism for this transformation. Computational analysis indicates the occurrence of an initial single electron transfer (SET) to 5-(trifluoromethyl)dibenzothiophenium triflate (TDTT), producing a transient L1−NiIII/CF3. adduct, which rapidly recombines to form a [L1-NiIV-CF3](X)2 intermediate species. A final facile reductive elimination affords L1−CF3. The well-defined square-planar model system studied here permits to gain fundamental knowledge on the rich redox chemistry of nickel, which is sought to facilitate the development of new Ni-based trifluoromethylation methodologies.

Item Type: Article
Additional Information: ** From Crossref via Jisc Publications Router. ** Licence for this article starting on 07-08-2017:
Uncontrolled Keywords: General Chemistry
Research Institute, Centre or Group - Does NOT include content added after October 2018: Biomedical Research Centre
Identification Number:
Page Range: 11662-11668
SWORD Depositor: Jill Hazard
Depositing User: Jill Hazard
Date Deposited: 14 Aug 2017 09:36
Last Modified: 18 Mar 2021 07:24

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