Chromium(VI) Oxyfluoride Dianions, [Cr O F ] and [CrO F ] ; Syntheses and Structures of [XeF ] [Cr O F ], [XeF ] [Cr O F ] ⋅ nX (X=HF, n=4; X=XeOF , n=2), and [XeF ][Xe F ][CrO F ].

The fluorobasic character of the strong oxidative fluorinator, XeF , and the oxidative resistance of the [XeF ] and [Xe F ] cations have been exploited for the syntheses of several novel Cr(VI) dianion salts. The reactions of XeF and CrO F in anhydrous HF and by direct fusion of the reactants in melts have yielded the first dinuclear Cr(VI) oxyfluoro-dianion salts, [XeF ] [Cr O F ], [XeF ] [Cr O F ] ⋅ 4HF, [XeF ] [Cr O F ] ⋅ 2XeOF , and mononuclear Cr(VI) oxyfluoro-dianion salt, [XeF ][Xe F ][CrO F ]. The salts were structurally characterized by low-temperature (LT) single-crystal X-ray diffraction (SCXRD) and LT Raman spectroscopy. The [CrO F ] and [Cr O F ] dianions have distorted octahedral cis-dioxo Cr(VI) coordination spheres in which two F-atoms are trans to one another and two F-atoms are trans to O-atoms, where the [Cr O F ] dianion is the fluorine-bridged dimer of the [CrO F ] anion. Quantum-chemical calculations were used to obtain the energy-minimized, gas-phase geometries, and the calculated vibrational spectra of the gas-phase dianions and their ion-pairs, which were used to aid in the vibrational frequency assignments of the crystalline salts. NBO and MEPS analyses and SCXRD show these salts are comprised of intimate ion-pairs in which their cations and anions interact through primarily electrostatic Xe- - -F σ-hole bonds.