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FBpin and its Adducts and their Role in Catalytic Borylations


We present herein investigations concerning the reactivity of B2pin2 and FBpin (pin = pinacolato) with respect to fluoride ions and NHCs (NHC = N Heterocyclic Carbene) in order to understand better the role of added fluoride in our recently reported Ni-catalyzed C-F borylation process, to confirm the nature of NHC-adducts of FBpin, and to explain the formation of species detected as side products of the defluoroborylation reaction. We report calculated gas phase fluoride ion affinities (FIA) of relevant boron species and demonstrate that the presence of one equivalent of added F in solution will bind and activate B2pin2 (FIA = +247 kJ·mol−1), but it will also bind even more effectively to FBpin (FIA = +287 kJ·mol−1) formed in the reaction. We prepared NHC-adducts of FBpin by two different methods and isolated and characterized several examples of the type FBpin∙NHC (NHC = iPr2Im, 1; Me2Im, 2; MeiPrIm, 3; nPr2Im, 4; Mes2Im 5). The salts [pinBF2][NMe4] 6, as well as the significantly more soluble analogue [pinBF2][NnBu4] 7 were also isolated and characterized, providing confirmation of the presence of the pinBF2 anion in various stoichiometric and catalytic borylation reactions.

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Publication details

The article was received on 30 Apr 2019, accepted on 07 Jun 2019 and first published on 07 Jun 2019

Article type: Paper
DOI: 10.1039/C9FD00053D
Faraday Discuss., 2019, Accepted Manuscript

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    FBpin and its Adducts and their Role in Catalytic Borylations

    L. Kuehn, M. Stang, S. Würtemberger-Pietsch, A. Friedrich, H. Schneider, U. Radius and T. B. Marder, Faraday Discuss., 2019, Accepted Manuscript , DOI: 10.1039/C9FD00053D

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