Elusive Antimony-Centered Radical Cations: Isolation, Characterization, Crystal Structures, and Reactivity Studies

Abstract

One-electron oxidation of the stibines Aryl₃ Sb (1, Aryl=2,6-ⁱ Pr₂ -4-OMe-C₆ H₂ ; 2, Aryl=2,4,6-ⁱ Pr₃ -C₆ H₂ ) with AgSbF₆ and NaBAryl^F₄ (Aryl^F =3,5-(CF₃ )₂ C₆ H₃ ) afforded the first structurally characterized examples of antimony-centered radical cations 1^.+ [BAryl^F₄ ]^- and 2^.+ [BAryl^F₄ ]^- . Their molecular and electronic structures were investigated by single-crystal X-ray diffraction, electron paramagnetic resonance spectroscopy (EPR) and UV/Vis absorption spectroscopy, in conjunction with theoretical calculations. Moreover, their reactivity was investigated. The reaction of 2^.+ [BAryl^F₄ ]^- and p-benzoquinone afforded a dinuclear antimony dication salt 3²⁺ [BAryl^F₄ ]₂^- , which was characterized by NMR spectroscopy and X-ray diffraction analysis. The formation of the dication 3²⁺ further confirms that the isolated stibine radical cations are antimony-centered.

Keywords: DFT calculations; EPR; antimony; radical cations; stibine.