page_title: Brookhart's acid
section_title: Structure and properties
hierarchical_section_title: Brookhart's acid / Structure and properties
caption_attribution_description: English: Crystal Structure of [H(Et2O)2][B(C6F5)4]
context_page_description: Brookhart's acid is the salt of the diethyl ether oxonium ion and tetrakis[3,5-bisphenyl]borate. It is a colorless solid, used as a strong acid. The compound was first reported by Volpe, Grant, and Brookhart in 1992.
context_section_description: The acid crystallizes as a white, hygroscopic crystalline solid. NMR and elemental analysis showed that the crystal contains two equivalents of diethyl ether. In solution, the compound slowly degrades to m-C₆H₃(CF₃)₂ and BAr′₃.
  [H(OEt₂)₂][B(C₆F₅)₄] is a related compound with a slightly different weakly coordinating anion; it was first reported in 2000.  An X-ray crystal structure of that compound was obtained, showing the acidic proton coordinated by both ethereal oxygen centers, although the crystal was not good enough to determine whether the proton is located symmetrically or unsymmetrically between the two.
caption: The crystal structure of the compound [H(OEt2)2][B(C6F5)4],[2] that is closely related to Brookhart's acid.  The acidic proton, which resides between the ether oxygen centres, is not shown.
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