Gold at ∼20 °C with F2 in anhydrous hydrogen fluoride (aHF) acidified with SbF5 dissolves to a red solution from which orange AuII(SbF6)2 crystallizes on removal of volatiles. Au(SbF6)2 is triclinic with a = 5.300(1) Å, b = 5.438(1) Å, c = 8.768(2) Å, α = 76.872(3)°, β = 88.736(3)°, γ = 68.109(3)°, V = 227.79(7) Å3, and Z = 1, space group P1̄. Each Au(II) atom, at 1̄, is at the center of an elongated octahedron of F ligands; the four F's of the approximately square AuF4 unit are at 2.09(2) Å × 2 Å and 2.15(2) Å × 2, each F provided by a different SbF6 species. The two long Au−F interatomic distances are at 2.64(2) Å. The SbF6 are grossly distorted in their interactions with the Au. A cis pair of F ligands of each SbF6, make close approach to two different gold atoms, stretching Sb−F to 1.99(2) and 1.94(2) Å. In each case the Sb−F distances trans to these stretched Sb−F bonds are short, being 1.85(2) and 1.84(2) Å, respectively. Magnetic susceptibility measurements show antiferromagnetic coupling with a susceptibility decrease below 13 K. Solvolysis of AuII(SbF6)2 in aHF is accompanied by disproportionation:  4Au(SbF6)2 → Au + Au3F8 + 8SbF5(solv). Fluorination, at ∼20 °C, of the solution of Au(SbF6)2, in SbF5 acidified aHF, precipitates red crystals of triclinic AuII{SbF6}2AuII{AuIIIF4}2 with a o = 5.2345(2) Å, b o = 8.1218(1) Å, c o = 10.5977(3) Å, α = 100.090(2)°, β = 100.327(2)°, γ = 104.877(2)°, V = 416.63(2) Å3, space group P1̄, and Z = 1. It is a simple paramagnet. The structure shows two different Au(II) environments, each approximately square-coordinated by F ligands, one being coordinated trans by an F ligand of each of two SbF6 and similarly by an F ligand from each of two AuIIIF4 species. The other Au(II) is approximately square-coordinated via bridging F ligands to four different AuIIIF4 species. AuII{SbF6}2AuII{AuIIIF4}2 with KAuF4 in aHF yields Au3F8 free of metallic gold, the simple paramagnetism of which indicates the formulation AuII{AuIIIF4}2.

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The molecular structures of WF6, ReF6, OsF6, IrF6, and PtF6 have been measured by electron diffraction from the gases, the last from both PtF6 itself and from a vapor assumed to consist of a mixture of O2 and PtF6 obtained by heating the salt O2PtF6. For models of Oh symmetry the bond lengths in the first three members of the series are essentially identical, but the Ir-F and Pt-F bonds are respectively about 0.01 and 0.02 A longer. Models of D4h symmetry were also tested for ReF6, OsF6, and IrF6 in which operation of the Jahn-Teller effect is thought possible. For these models the same trend was seen in the average bond-length values. The effect of three-atom multiple scattering was also investigated, and experimental estimates of the effects of vibrational averaging ("shrinkage") on the distances were obtained. Normal-coordinate analyses based on the observed wavenumbers yielded stretching force constants consistent with the usual inverse bond-length/force-constant relationship. Ab initio molecular orbital optimizations of the molecules constrained to Oh symmetry were carried out at several levels of theory and basis-set size. Less extensive optimizations of ReF6, OsF6, and IrF6 with D4h symmetry were also carried out. The best overall agreement with both the experimental values and the distance trend for Oh symmetry was obtained with the Hay-Wadt (n+1)VDZ basis on the metals and the aug-cc-pVTZ on the fluorines at the MP2 level, but these bases with B3P86 and B3PW91 density functional theory were nearly as good and with B3LYP only slightly worse. The D4h structures for ReF6, OsF6, and IrF6 with the cited bases at the B3P86 level were slightly more stable (respectively 0.8, 2.6, and 1.4 kcal/mol) with the axial bonds shorter by about 0.04 A in ReF6 and 0.07 A in OsF6, but about 0.05 A longer in IrF6. The significance of these values is uncertain. The experimental bond lengths (rg/A) with estimated 2sigma uncertainties for the models of Oh symmetry are W-F = 1.829(2), Re-F = 1.829(2), Os-F = 1.828(2), Ir-F = 1.839(2), and Pt-F = 1.852(2); the Pt-F value from the O2PtF6 sample was 1.851(2) A. Although the experimental data neither confirm nor refute the existence of the Jahn-Teller effect in ReF6, OsF6, and IrF6, they ensure that if present the distortion from Oh symmetry must be small.