Synthesis and Characterization of CrF4O, KrF2, CrF4O, and NO+CrF5O-

摘要

Chromium(VI) tetrafluoride oxide can be prepared in high yield and purity from CrO2F2 and KrF2 in HF solution. The vibrational spectra of gaseous, solid, and matrix-isolated CrF4O and its BrF5 and Hf solutions are reported, as well as the 19F NMR spectra of the BrF5 and SO2C1F solutions. The data confirm for gaseous, matrix-isolated, and dissolved CrF4O a monomeric, square-pyramidal structure of symmetry C sub 4V and for solid CrF4O a fluorine-bridged polymeric structure. CrF4O is a strong Lewis acid, and witho FNO it forms a stable NO+CrF5O- salt, which was characterized by vibrational spectroscopy. With KrF2 it forms an unstable 1:1 adduct that has in the solid phase an essentially covalent structure containing a Kr-F---Cr bridge but is completely dissociated in SO2C1F solution. With AsF5 it does not form a stable adduct at temperatures as low as -78 c, indicating that CrF4O is a weak Lewis base. It was also shown that CrF30 is a weak Lewis base and does not form a stable adduct at -78 C.