Structure-constraint induced increase in Lewis acidity of tris(ortho-carboranyl)borane and selective complexation with Bestmann ylides

Libo Xiang; Junyi Wang; Alexander Matler; Qing Ye

doi:10.1039/d4sc06144f

Structure-constraint induced increase in Lewis acidity of tris(ortho-carboranyl)borane and selective complexation with Bestmann ylides

Chem Sci. 2024 Oct 4;15(43):17944-17949. doi: 10.1039/d4sc06144f. Online ahead of print.

Authors

Libo Xiang^{1

2}, Junyi Wang³, Alexander Matler^{1

2}, Qing Ye^{1

2}

Affiliations

¹ Institute for Inorganic Chemistry Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany [email protected].
² Institute for Sustainable Chemistry & Catalysis with Boron Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany.
³ Department of Chemistry, Southern University of Science and Technology 518055 Shenzhen P. R. China.

Abstract

The Lewis acidity of tris(ortho-carboranyl)borane has been slightly increased by mimicking the structural evolution from triarylborane to 9-aryl-9-borafluorene. The o-carborane-based analogue (C₂B₁₀H₁₀)₂B(C₂B₁₀H₁₁), obtained via salt elimination between LiC₂B₁₀H₁₁ and (C₂B₁₀H₁₀)₂BBr, has been fully characterized. Gutmann-Beckett and computational fluoride/hydride ion affinity (FIA/HIA) studies have confirmed the increase in Lewis acidity, which is attributable to structural constraint imposed by the CC-coupling between two carboranyl groups. Selective complexation of (C₂B₁₀H₁₀)₂B(C₂B₁₀H₁₁) with Bestmann ylides R₃PCCO (R = Ph, Cy) has been achieved, enabling further conversion into the zwitterionic phospholium salt through NHC-catalyzed proton transfer.