XeF2·2CrF4 and XeF5 +CrF5 -:  Syntheses, Crystal Structures, and Some Properties

XeF2·2CrF4 was prepared by solvolysis of XeF2·CrF4 in anhydrous hydrogen fluoride (aHF) and subsequent decantation of the majority of dissolved XeF2 in aHF. Remaining XeF2 and a large excess of CrF4 form XeF2·2CrF4 after aHF is removed. Ruby-red single crystals were obtained either by heating the sample in a thermal gradient or by recrystallization in supercritical SF6. The compound crystallizes in the triclinic space group P1̄ with a = 855.1(3) pm, b = 922.1(3) pm, c = 1043.8(3) pm, α = 76.02(2)°, β = 81.36(2)°, γ = 88.08(3)°, and Z = 4 at 293 K. The basic structural unit is formed by four independent Cr atoms, each octahedrally coordinated by six F atoms. Two fluorine ligands are provided by two different XeF2 molecules. The distorted octahedra are connected via common F atoms to form a three-dimensional network. XeF5 +CrF5 - was prepared from XeF6 and CrF4 at room temperature or by the reaction of XeF6 and CrF5 at 333 K. Red single crystals were grown from the solution of XeF5 +CrF5 - in aHF. The compound crystallizes in the orthorhombic space group Pbca with a = 1828.1(13) pm, b = 842.9(7) pm, c = 1852.1(12) pm, and Z =16 at 268 K. The main structural feature is formed by an infinite chain of distorted CrF6 octahedra joined via cis vertexes, while XeF5 + cations compensate the negative charge of each octahedron.