Ba₃Mg₄Au₄ – a ternary auride composed of BaAu₂- and BaMg₂Au-related slabs

The ternary auride Ba 3 Mg 4 Au 4 was synthesized from the elements in a sealed tantalum ampoule. The Ba 3 Mg 4 Au 4 structure was refined from single-crystal X-ray diffractometer data: Gd 3 Cu 4 Ge 4 type, space group Immm , a = 447.95(10), b = 843.07(18), c = 1564.2(5) pm, wR 2 = 0.0935, 680 F 2 values, 23 variables. Ba 3 Mg 4 Au 4 is a 1:2 intergrowth structure of BaAu 2 -(AlB 2 type) and BaMg 2 Au-(MgCuAl 2 type) related slabs. The two crystallographically independent gold atoms both have tricapped trigonal prismatic coordination, i.e. Au1@Mg 6 Ba 3 and Au2@Mg 2 Ba 6 Au. The Au–Mg (284–303 pm) and Ba–Au (331–349 pm) distances cover small ranges that are close to the sums of the covalent radii. The magnesium atoms in the MgCuAl 2 -related slab show Mg–Mg distances of 320–332 pm. The different coloring variants of the Gd 3 Cu 4 Ge 4 type are briefly discussed.