Protonation of Borylated Carboxonium Derivative [2,6-B10H8O2CCH3]-: Theoretical and Experimental Investigation

Abstract

The process of protonation of [2,6-B₁₀H₈O₂CCH₃]^- was investigated both theoretically and experimentally. The most suitable conditions for protonation of the derivative [2,6-B₁₀H₈O₂CCH₃]^- were found. The process of protonation was carried out in the presence of an excess of trifluoromethanesulfonic acid CF₃SO₃H at room temperature in dichloromethane solution. The structure of the resulting complex [2,6-B₁₀H₈O₂CCH₃*H^fac]⁰ was established using NMR data and the results of DFT calculations. An additional proton atom H^fac was found to be localized on one of the facets that was opposite the boron atom in a substituted position, and which bonded mainly with one apical boron atom. The main descriptors of the B-H^fac bond were established theoretically using QTAIM and NBO approaches. In addition, the mechanism of [2,6-B₁₀H₈O₂CCH₃]^- protonation was investigated.

Keywords: DFT calculation; Fukui function; NMR spectra; QTAIM; boron cluster; closo-borates; protonation.