The crystal structure of xenon(II) fluoride fluorosulfate has been determined from three-dimensional X-ray data. The compound crystallizes in the orthorhombic system, with eight molecules in a unit cell of dimensions a = 9.88 (1), b = 10.00 (1), and c = 10.13 (1) A. The space group is Pbca. and refinement has proceeded satisfactorily in this space group, with a final conventional R factor of 0.045 for 838 nonzero reflections. The structure analysis has established the existence of discrete FXeOSChF molecules. The xenon atom is approximately linearly coordinated by an oxygen atom of the fluorosulfate group and a fluorine atom. The angle F-Xe-0 is 177.4 (3)°, and the interatomic distances are Xe-F = 1.940 ( 8) and Xe-0 = 2.155 (8) A. The fluorosulfate group is similar to that observed in the alkali salts, with the difference that, in this structure, the group is distorted as a consequence of one oxygen atom being linked to the xenon atom. This oxygen atom is longer bonded to the sulfur atom and subtends lower angles to its neighboring atoms of the -OSChF group than the other oxygen atoms.

The fluorine ligands of xenon difluoride may be substituted, one at a time, by other electronegative species. Interaction of the difluoride with the appropriate molar quantity of anhydrous acid, below 0°, yields. the monofluorosulfate, FXeOS0 2 F, which is a colorless solid, m.p. 36.6°, the bis-fluorosulfate, Xe(OS0 2 F) 2 , whichis a pale yellow solid, m.p. 43-450, ~he mon8perchlorate, FXeOClOg' which is a colorless solid, m.p. 16.5° and a yellow solid, which decomposes belo-v1 0°, which is probably the bisperchlorate, Xe(OCl0 3) 2. All of these xenon difluoride derivatives are thermodynamically unstable and dismutate spontaneously above 0°, the • .

Xenon difluoride forms a 1:1 complex with XeOF4 (m.p. 29°C) which is isostructural with XeF2 · IF5. The unit cell is tetragonal with a = 7.56(2), c = 11.36(3) Å, V = 647 Å3, z = 4. RAMAN data prove it to be a molecular complex, the structure of which is compatible with appreciable bond polarity in XeF2. Similar interactions of XeF2 with the XeF+5 cation are indicated by the RAMAN spectra of the complexes which XeF2 forms with [XeF5]+[AsF6]−. The spectrum of the 1:2 complex indicates that the XeF2 molecule is undistorted but the spectrum of the 1:1 complex suggests that the XeF2 molecule is distorted by interaction with XeF+5 ions. The occurrence of molecular XeF2 in the XeF+5AsF6 lattice confirms the superiority of XeF6 to XeF2 as a fluoride ion donor.

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