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.