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 XeF 6 and Cr VI OF 4 in 1:1 and 1:2 molar ratios undergo reduction to Cr(V) and Cr(IV) by means of F 2 elimination to form [XeF 5 ][Xe 2 F 11 ][Cr V OF 5 ]∙2Cr VI OF 4 and [XeF 5 ] 2 [Cr IV F 6 ]∙2Cr VI OF 4 , respectively, as shown by low-temperature (LT) single-crystal X-ray diffraction (SCXRD). A LT Raman spectroscopic study of an equimolar mixture of solid XeF 6 and CrOF 4 and its melt showed that [Cr VI OF 5 ] – is formed as an intermediate. Reaction of [XeF 5 ] 2 [Cr IV F 6 ]∙2Cr VI OF 4 with XeF 6 in a melt gave [Xe 2 F 11 ] 2 [Cr IV F 6 ] and [XeF 5 ] 2 [Cr V 2 O 2 F 8 ]. Their LT crystal structures revealed that [XeF 5 ] + and [Xe 2 F 11 ] + are coordinated to their respective [CrF 6 ] 2− and [Cr 2 O 2 F 8 ] 2− anions by means of Xe---F–Cr bridges to form infinite chain structures. The reactions of a 1:1 molar ratio of XeF 6 and CrOF 4 in anhydrous hydrogen fluoride (aHF) and in mixed CFCl 3 /aHF solvents yielded [XeF 5 ] 2 [Cr V 2 O 2 F 8 ]∙2HF and a mixture of [XeF 5 ] 2 [Cr V 2 O 2 F 8 ]∙2HF and [XeF 5 ] 2 [Cr V 2 O 2 F 8 ]∙2XeOF 4 , respectively. The SCXRD structures of the latter and aforementioned salts provide the first X-ray structures of [CrOF 5 ] 2– and [Cr 2 O 2 F 8 ] 2– . The [XeF 5 ] 2 [Cr V 2 O 2 F 8 ]∙2XeOF 4 and [XeF 5 ][Xe 2 F 11 ][Cr V OF 5 ]∙2Cr VI OF 4 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 [Cr VI OF 5 ] – , [XeF 5 ] 2 [Cr V 2 O 2 F 8 ]∙2XeOF 4 , [Cr V 2 O 2 F 8 ] 2– , [XeF 5 ][Xe 2 F 11 ][Cr V OF 5 ]∙2Cr VI OF 4 , [Cr V OF 5 ] 2– , and to aid in the assignments of their vibrational frequencies.