Synthesis of Au(II) Fluoro Complexes and Their Structural and Magnetic Properties

Gold at ∼20 °C with F 2 in anhydrous hydrogen fluoride (aHF) acidified with SbF 5 dissolves to a red solution from which orange Au II (SbF 6 ) 2 crystallizes on removal of volatiles. Au(SbF 6 ) 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) Å 3, and Z = 1, space group P 1̄. 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 AuF 4 unit are at 2.09(2) Å × 2 Å and 2.15(2) Å × 2, each F provided by a different SbF 6 species. The two long Au−F interatomic distances are at 2.64(2) Å. The SbF 6 are grossly distorted in their interactions with the Au. A cis pair of F ligands of each SbF 6, 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 Au II (SbF 6 ) 2 in aHF is accompanied by disproportionation: 4Au(SbF 6 ) 2 → Au + Au 3 F 8 + 8SbF 5 (solv). Fluorination, at ∼20 °C, of the solution of Au(SbF 6 ) 2, in SbF 5 acidified aHF, precipitates red crystals of triclinic Au II {SbF 6 } 2 Au II {Au III F 4 } 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) Å 3, space group P 1̄, 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 SbF 6 and similarly by an F ligand from each of two Au III F 4 species. The other Au(II) is approximately square-coordinated via bridging F ligands to four different Au III F 4 species. Au II {SbF 6 } 2 Au II {Au III F 4 } 2 with KAuF 4 in aHF yields Au 3 F 8 free of metallic gold, the simple paramagnetism of which indicates the formulation Au II {Au III F 4 } 2 .