The intermetallic barium compounds Ba T Mg 2 ( T = Pd, Ag, Pt, Au) and BaAuCd 2 were synthesized by reactions of the elements in sealed tantalum ampoules in muffle furnaces. The five compounds crystallize with the orthorhombic MgCuAl 2 type structure, space group Cmcm , with small differences in chemical bonding between the magnesium and cadmium series. All samples were characterized through their Guinier powder diffraction patterns. The structures of BaPdMg 2 ( a = 444.57(4), b = 1174.67(10), c = 827.58(7) pm, w R 2 = 0.0460, 475 F 2 values, 16 variables), BaAuMg 2 ( a = 450.27(6), b = 1183.94(16), c = 838.76(11) pm, w R 2 = 0.0355, 473 F 2 values, 16 variables) and BaAuCd 2 ( a = 463.31(5), b = 1112.79(12), c = 826.63(8) pm, w R 2 = 0.0453, 469 F 2 values, 16 variables) were refined from single crystal X-ray diffraction data. The large barium atoms push the [ T Mg 2 ] respectively [AuCd 2 ] substructures apart. This allows fast moisture attack and leads to fast hydrolyzes of the samples when they get in contact with water. The influence of the difference in electronegativity between magnesium and cadmium is reflected for the pair of compounds BaAuMg 2 and BaAuCd 2 . The magnesium compound shows the higher auridic character, while the cadmium compound shows a tendency towards a three-dimensional cadmium substructure.