Boroles from alumoles: accessing boroles with alkyl-substituted backbones via transtrielation

Josina L Bohlen; Lukas Endres; Regina Drescher; Krzysztof Radacki; Maximilian Dietz; Ivo Krummenacher; Holger Braunschweig

doi:10.1039/d3sc02668j

Boroles from alumoles: accessing boroles with alkyl-substituted backbones via transtrielation

Chem Sci. 2023 Jul 19;14(34):9010-9015. doi: 10.1039/d3sc02668j. eCollection 2023 Aug 30.

Authors

Josina L Bohlen^{1

2}, Lukas Endres^{1

2}, Regina Drescher^{1

2}, Krzysztof Radacki^{1

2}, Maximilian Dietz^{1

2}, Ivo Krummenacher^{1

2}, Holger Braunschweig^{1

2}

Affiliations

¹ Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany h.braunschweig@uni-wuerzburg.de.
² Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany.

Abstract

The alumole Cp^3tAlC₄Et₄ (Cp^3t = 1,2,4-tris(tert-butyl)cyclopentadienyl) is reported to be capable of transferring its butadiene moiety to aryl(dihalo)boranes to generate boroles through aluminum-boron exchange. The products feature a rare alkyl-substituted backbone, which, as shown in other examples, often leads to dimerization due to insufficient steric protection of the antiaromatic borole ring. Sterically crowded aryl groups bound to the boron atom are shown to prevent dimerization, allowing access to the first monomeric derivatives of this type. Results from UV-vis spectroscopy, electrochemistry, and DFT calculations reveal that the alkyl substituents cause remarkable modifications in the optical and electronic properties of the boroles compared to their perarylated counterparts.