New evidence in an old case: the question of chromium hexafluoride reinvestigated.

The question of whether or not the chromium hexafluoride molecule has been synthesized and characterized has been widely discussed in the literature and cannot, in spite of many efforts, yet be answered beyond doubt. New matrix-isolation experiments can now show, together with state-of-the-art quantum-chemical calculations, that the compound previously isolated in inert gas matrixes, was CrF5 and not CrF6. New bands in the matrix IR spectra can be assigned to the Cr2F10 dimer, and furthermore evidence was found in the spectra for a photodissociation or reversible excitation of CrF5 under UV irradiation. However, even if CrF6 is not stable at ambient conditions, its formation under high fluorine pressures in autoclave reactions cannot be excluded completely.