Reactivity of cyano- and isothiocyanatoborylenes: metal coordination, one-electron oxidation and boron-centred Brønsted basicity. Issue 22 (11th May 2021)

• Record Type: Journal Article
• Authors: Hagspiel, Stephan; Elezi, Dren; Arrowsmith, Merle; Fantuzzi, Felipe; Vargas, Alfredo; Rempel, Anna; Härterich, Marcel; Krummenacher, Ivo; Braunschweig, Holger
• Is Part Of: Chemical science. Volume 12:Issue 22(2021)
• Page Start: 7937
• Page End: 7942
• Publication Date: 2021-05-11
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1sc01580j
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Borylenes of the form (CAAC)(NHC)BY (Y = CN, NCS; CAAC = cyclic alkyl(amino)carbene; NHC = N-heterocyclic carbene) coordinate to group 6 carbonyl complexes via Y, and show reversible boron-centered Brønsted basicity and one-electron oxidation. Abstract : Doubly base-stabilised cyano- and isothiocyanatoborylenes of the form LL′BY (L = CAAC = cyclic alkyl(amino)carbene; L′ = NHC = N-heterocyclic carbene; Y = CN, NCS) coordinate to group 6 carbonyl complexes via the terminal donor of the pseudohalide substituent and undergo facile and fully reversible one-electron oxidation to the corresponding boryl radical cations [LL′BY]˙ + . Furthermore, calculations show that the borylenes have very similar proton affinities, both to each other and to NHC superbases. However, while the protonation of LL′B(CN) with PhSH yielding [LL′BH(CN) + ][PhS − ] is fully reversible, that of LL′B(NCS) is rendered irreversible by a subsequent B-to-CCAAC hydrogen shift and nucleophilic attack of PhS − at boron.