Chromium Oxide Tetrafluoride and Its Reactions with Xenon Hexafluoride; the [XeF5]+ and [Xe2F11]+ Salts of the [CrVIOF5]-, [CrVOF5]2-, [CrV2O2F8]2-, and [CrIVF6]2- Anions

Molten mixtures of XeF6 and (CrOF4)-O-VI react by means of F-2 elimination to form [XeF5][Xe2F11][(CrOF5)-O-V]2 (CrOF4)-O-VI, [XeF5](2)[(CrF6)-F-IV]2 (CrOF4)-O-VI, [Xe2F11](2)[(CrF6)-F-IV], and [XeF5](2)[(Cr2O2F8)-O-V], whereas their reactions in anhydrous hydrogen fluoride (aHF) and CFCl3/aHF yield [XeF5](2)[(Cr2O2F8)-O-V]2 HF and [XeF5](2)[(Cr2O2F8)-O-V]2 XeOF4. Other than [Xe2F11][(MOF5)-O-VI] and [XeF5][(M2O2F9)-O-VI] (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 [XeF5](+) and/or [Xe2F11](+) salts of the known [(CrOF5)-O-V](2-) and [(CrF6)-F-IV](2-) anions, and the novel [(Cr2O2F8)-O-V](2-) anion. A low-temperature Raman spectroscopic study of an equimolar mixture of solid XeF6 and CrOF4 revealed that [Xe2F11][(CrOF5)-O-VI] 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 [(CrOF5)-O-V](2-) and [(Cr2O2F8)-O-V](2-) anions, where [(Cr2O2F8)-O-V](2-) represents a new structural motif among the known oxyfluoro-anions of Group 6. The X-ray structures show that [XeF5](+) and [Xe2F11](+) 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.