The hydrogen fluoride solvent system. Part VI. Solutions of hydrogen cyanide, silver(I) cyanide, and hexacyanoferric(II) acid: formation of the difluoromethylammonium cation

Abstract

Hydrogen cyanide, a non-electrolyte in anhydrous hydrogen fluoride, is protonated in the presence of boron tri-fluoride and arsenic pentafluoride. Unstable solids believed to be HCNH⁺BF₄^– and HCNH⁺AsF₆^– have been prepared. In solution in hydrogen fluoride, hydrogen cyanide slowly adds HF to form the cation F₂HC·NH₃⁺, which has been isolated as the AsF₆^– salt. Further slow reaction occurs in solution to form a polymer containing CF₂H·NH groups. Conductimetric titrations of silver(I) cyanide and hexacyanoferric(II) acid with BF₃ show that neither solute liberates HCN in this solvent; hexacyanoferric(II) acid forms Fe(HCN)₆²⁺.