Vaporization and vapor complexation in the gold(III) chloride-aluminum(III) chloride system

Article abstract of DOI:10.1021/ic00036a010

The vapors over solid gold(III) chloride and the vapor-phase equilibria of the gold(III) chloride-alummum(III) chloride binary system have been investigated spectrophotometrically. The thermodynamic functions of the sublimation 2AuCl₃(s) = Au₂Cl₆(g) were determined: ΔH_S° = 114.2 ± 1.8 kJ mol^-1 and ΔS_S° = 160.5 ± 3.3 J mol^-1 K^-1 (480 < T < 580K). One predominant vapor complex found in the binary system formed according to the reaction AuCl₃(s) + ¹/₂Al₂Cl₆(g) = AuAlCl₆(g) with ΔH_R° = 59.9 ± 0.8 kJ mol^-1 and ΔS_R° = 91.5 ± 1.6 J mol^-1 K^-1 (470 < T < 550 K). At 470 K and 1 atm Al₂Cl₆(g) pressure the volatility enhancement of AuCl₃ is ～300. The electronic absorption spectra of the Au₂Cl₆(g) and AuAlCl₆(g) molecules were interpreted in terms of a distorted square planar geometry of Au(III). Bridged and terminal ligand-to-metal charge-transfer bands were indentified in the spectra.