10049-11-3

NF4CrF6, a new stable NF4+ salt containing an energetic counterion, was prepared by treatment of CrF5 with an excess of NF4HF2 in HF solution. The composition and ionic nature of NF4CrF6 was established by elemental analysis, vibrational and 19F NMR spectroscopy, and its X-ray powder pattern. Reactions of CrF5 with H2O in HF, ClF3, FNO, Cl2, CFCl3, and KrF2 were studied to determine its acidity and oxidizing power. With FNO, a stable 1:1 adduct is formed, which on the basis of its vibrational spectra has the ionic structure NO+CrF6-. The reaction of NOCrF6 with NO produced (NO+)2CrF62-, which by controlled pyrolysis was converted to NO+CrF5-. With stoichiometric amounts of H2O in HF, CrF5 did not form a stable OH3+CrF6- salt but the reaction resulted in hydrolysis to CrF3O. The influence of the strong Lewis acids AsF5 and SbF5 on the oxidizing power of CrF5 was also investigated. On the basis of the fact that CrF5-SbF5 mixtures can oxidize O2 (IP = 12.06 eV) but not NF3 (IP = 13.00 eV), the following qualitative oxidizer strength scale is proposed: KrF+ > PtF6 > SbF5 + F2 + activation energy > CrF5-SbF5. The results of a normal-coordinate analysis of CrF6- and CrF62- show the expected decrease in force constants with increasing negative charge.