Chromium Oxide Tetrafluoride and Its Reactions with Xenon Hexafluoride; the [XeF5]+ and [Xe2F11]+ Salts of the [Cr(VI)OF5]–, [Cr(IV)F6]2–, [Cr(V)OF5]2–, and [Cr(V)2O2F8]2– Anions
Molten mixtures of XeF6 and CrVIOF4 in 1:1 and 1:2 molar ratios undergo reduction to Cr(V) and Cr(IV) by means of F2 elimination to form [XeF5][Xe2F11][CrVOF5]∙2CrVIOF4 and [XeF5]2[CrIVF6]∙2CrVIOF4, respectively, as shown by low-temperature (LT) single-crystal X-ray diffraction (SCXRD). A LT Raman spectroscopic study of an equimolar mixture of solid XeF6 and CrOF4 and its melt showed that [CrVIOF5]– is formed as an intermediate. Reaction of [XeF5]2[CrIVF6]∙2CrVIOF4 with XeF6 in a melt gave [Xe2F11]2[CrIVF6] and [XeF5]2[CrV2O2F8]. Their LT crystal structures revealed that [XeF5]+ and [Xe2F11]+ are coordinated to their respective [CrF6]2− and [Cr2O2F8]2− anions by means of Xe---F–Cr bridges to form infinite chain structures. The reactions of a 1:1 molar ratio of XeF6 and CrOF4 in anhydrous hydrogen fluoride (aHF) and in mixed CFCl3/aHF solvents yielded [XeF5]2[CrV2O2F8]∙2HF and a mixture of [XeF5]2[CrV2O2F8]∙2HF and [XeF5]2[CrV2O2F8]∙2XeOF4, respectively. The SCXRD structures of the latter and aforementioned salts provide the first X-ray structures of [CrOF5]2– and [Cr2O2F8]2–. The [XeF5]2[CrV2O2F8]∙2XeOF4 and [XeF5][Xe2F11][CrVOF5]∙2CrVIOF4 salts were also characterized by LT Raman spectroscopy. Quantum-chemical calculations were carried out to obtain the energy-minimized, gas-phase geometries and vibrational frequencies for [CrVIOF5]–, [XeF5]2[CrV2O2F8]∙2XeOF4, [CrV2O2F8]2–, [XeF5][Xe2F11][CrVOF5]∙2CrVIOF4, [CrVOF5]2–, and to aid in the assignments of their vibrational frequencies.