Synthesis, crystal structure as well as IR-and Ramanspectroscopic properties of the new ternary azidoaurates(III) A[Au(N 3 ) 4 ] (A ϭ K, Rb, Cs) are reported. The translucent orangered compounds were prepared by reaction of the respective binary azides with HAuCl 4 in aqueous solutions at room temperature. The crystal structures determined by single crystal X-ray diffraction methods are monoclinic 1671 and provide the first examples for azidoaurates with mono-atomic cations. The unusual reduction of the lattice parameter a with increasing cation size in the isotypic series is discussed in detail. IRand Raman-spectroscopic measurements show strongly covalent gold-nitrogen contacts, a bonding situation which is further supported by quantum chemical calculations and ELF-analyses. prepare binary alloys, e.g. NaAu 2 [9]. In this study, the influence of cation size on the crystal structure, the shape of the azidoaurate anions, and the spectroscopic properties have been investigated in detail.
Experimental SectionDue to the potentially explosive nature of the compounds under investigation, all handlings were carried out under extreme caution. It was especially important to prevent shock, heat, and intense radiation, as well as handling the products with metallic objects. Binary azides, KN 3 , RbN 3 , and CsN 3 , were synthesized from NaN 3 (Roth, 99.9 %, recrystallized in water) and the corresponding carbonates A 2 CO 3 (A ϭ K, Rb, Cs, all Alfa, 99.9 %) by ion-exchange methods in water. The resin column (l ϭ 775 mm, л i ϭ 14.2 mm) was filled with acidic cation-exchange resin (Merck), and ion-exchange was performed with a 5 ml·min Ϫ1 flow rate of HN 3 . The white product was collected after evaporation of the solvent. Alkali metal azidoaurates, A[Au(N 3 ) 4 ] (A ϭ K, Rb, Cs; in the further text referred to as: A ϭ A[Au(N 3 ) 4 ], K ϭ K[Au(N 3 ) 4 ], Rb ϭ Rb[Au(N 3 ) 4 ], Cs ϭ Cs[Au(N 3 ) 4 ]), were synthesized by reaction of the binary azides with HAuCl 4 (Alfa). The starting materials were dissolved in water or ethanol, the solutions were mixed with a slight excess of the alkali azide according to (1) and kept for 12 Ϫ 24 hours in a slightly tilted petri dish. Temperature treatment experiments were performed using either a heat plate or an ice bath in the range of 273 K Ϫ 323 K. Orange-red, brittle and often twinned crystals which are highly explosive when exposed to pressure, heat, or intense radiation were obtained during evaporation of the sol-
