Boron radical cations: facile oxidation of electron rich diborenes

Bissinger, Philipp, Braunschweig, Holger, Damme, Alexander, Kupfer, Thomas, Krummenacher, Ivo and Vargas, Alfredo (2014) Boron radical cations: facile oxidation of electron rich diborenes. Angewandte Chemie International Edition, 53 (22). pp. 5689-5693. ISSN 1433-7851

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The realization of a phosphine-stabilized diborene, Et3P⋅(Mes)B=B(Mes)⋅PEt3 (4), by KC8 reduction of Et3P⋅B2Mes2Br2 in benzene enabled the evaluation and comparison of its electronic structure to the previously described NHC-stabilized diborene IMe⋅(Dur)B=B(Dur)⋅IMe (1). Importantly, both species feature unusual electron-rich boron centers. However, cyclic voltammetry, UV/Vis spectroscopy, and DFT calculations revealed a significant influence of the Lewis base on the reduction potential and absorption behavior of the B-B double bond system. Thus, the stronger σ-donor strength and larger electronegativity of the NHC ligand results in an energetically higher-lying HOMO, making 1 a stronger neutral reductant as 4 (1: E1/2=−1.55 V; 4: −1.05 V), and a smaller HOMO–LUMO gap of 1 accompanied by a noticeable red-shift of its lowest-energy absorption band with respect to 4. Owing to the highly negative reduction potentials, 1 and 4 were easily oxidized to afford rare boron-centered radical cations (5 and 6).

Item Type: Article
Schools and Departments: School of Life Sciences > Chemistry
Subjects: Q Science > QD Chemistry
Depositing User: Alfredo Vargas
Date Deposited: 10 Apr 2014 09:08
Last Modified: 14 Aug 2014 15:53
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