Chromium Oxide Tetrafluoride and Its Reactions with Xenon Hexafluoride; the [XeF ] and [Xe F ] Salts of the [Cr OF ] , [Cr OF ] , [Cr O F ] , and [Cr F ] Anions.

Molten mixtures of XeF and Cr OF react by means of F elimination to form [XeF ][Xe F ][Cr OF ]⋅2 Cr OF , [XeF ] [Cr F ]⋅2 Cr OF , [Xe F ] [Cr F ], and [XeF ] [Cr O F ], whereas their reactions in anhydrous hydrogen fluoride (aHF) and CFCl /aHF yield [XeF ] [Cr O F ]⋅2 HF and [XeF ] [Cr O F ]⋅2 XeOF . Other than [Xe F ][M OF ] and [XeF ][M O F ] (M=Mo or W), these salts are the only Group 6 oxyfluoro-anions known to stabilize noble-gas cations. Their reaction pathways involve redox transformations that give [XeF ] and/or [Xe F ] salts of the known [Cr OF ] and [Cr F ] anions, and the novel [Cr O F ] anion. A low-temperature Raman spectroscopic study of an equimolar mixture of solid XeF and CrOF revealed that [Xe F ][Cr OF ] is formed as a reaction intermediate. The salts were structurally characterized by LT single-crystal X-ray diffraction and LT Raman spectroscopy, and provide the first structural characterizations of the [Cr OF ] and [Cr O F ] anions, where [Cr O F ] represents a new structural motif among the known oxyfluoro-anions of Group 6. The X-ray structures show that [XeF ] and [Xe F ] form ion pairs with their respective anions by means of Xe- - -F-Cr bridges. Quantum-chemical calculations were carried out to obtain the energy-minimized, gas-phase geometries and the vibrational frequencies of the anions and their ion pairs and to aid in the assignments of their Raman spectra.