The Gold Sulfates MAu(S0₄)₂ (M = Na, K, Rb)

The evaporation of a solution of Au(OH) 3 and Na 2 So 4 in conc. sulfuric acid led to yellow single crystals of NaAu(SO 4 ) 2 (monoclinic, P2 1 /n, Z = 2, a = 469.1, b = 845.9, c = 831.2 pm, β = 95.7°). Analogous procedures with K 2 SO 4 or Rb 2 SO 4 instead of Na 2 SO 4 yielded single crystals of KAu(SO 4 ) 2 (monoclinic, C2/c, Z = 4, a = 1109.8, b = 724.2, c = 941.1 pm, β = 118.4°) and RbAu(S04)2, respectively, (triclinic, P1̄, Z = 1, a = 423.6, b = 497.5, c = 889.0 pm, a = 76.4°, β = 88.4°, γ = 73.5°). Although the crystal structures of the three sulfates are not isotypic they show similar structural features: The gold atoms are coordinated by four oxygen atoms in a square planar manner. These oxygen atoms belong to four SO 4 2- ions which link the [AUO 4 ] units to infinite chains according to 1 ∞ [Au(SO 4 ) 4/ 2 ] - . These chains are connected via the monovalent cations which show coordination numbers of 6 (Na + ), 10 (K + ) and 12 (Rb + ), respectively.