Tris(perfluorotolyl)borane—A Boron Lewis Superacid

Abstract

Tris[tetrafluoro-4-(trifluoromethyl)phenyl]borane (BTolF) was prepared by treating boron tribromide with tetrameric F₃ CC₆ F₄ -Cu^I . The F₃ CC₆ F₄ -Cu^I was generated from F₃ CC₆ F₄ MgBr and copper(I) bromide. Lewis acidities of BTolF evaluated by the Gutmann-Beckett method and calculated fluoride-ion affinities are 9 and 10 %, respectively, higher than that of tris(pentafluorophenyl)borane (BCF) and even higher than that of SbF₅ . The molecular structures of BTolF and BCF were determined by gas-phase electron diffraction, that of BTolF also by single-crystal X-ray diffraction.