The rare earth metal-rich compounds RE4IrMg (RE = Y, La, Pr, Nd, Sm, Gd, Tb, Dy) and RE23Ir7Mg4 (RE = La, Ce, Pr, Nd) were synthesized from the elements in sealed tantalum tubes in an induction furnace. Several structures were investigated on the basis of X-ray single crystal diffraction: P63mc, Z = 2, a = 1001.2(7), c = 2257.2(5) pm, wR2 = 0.0441, 2402 F2 values, 74 variables for Pr23Ir6.81Mg4, Gd4RhIn type, , Z = 16, a = 1438.3(2) pm, wR2 = 0.0490, 542 F2 values, for La4IrMg, a = 1405.6(2) pm, wR2 = 0.0368, 451 F2 values, for Nd4IrMg, a = 1381.2(2) pm, wR2 = 0.0541, 480 F2 values, for Gd4IrMg, a = 1370.7(2) pm, wR2 = 0.0377, 392 F2 values, for Tb4IrMg with 19 variables per refinement. All other compounds have been characterized by X-ray powder diffraction data. Pr23Ir6.81Mg4 crystallizes with a new structure type. The three crystallographically independent iridium atoms have trigonal prismatic praseodymium coordination with short Ir-Pr distances ranging from 285 to 300 pm. The trigonal prisms are condensed to a three-dimensional network via common edges and corners. Voids in the network are filled by the coordination polyhedra of the Pr4 and Pr6 atoms and Mg4 tetrahedra (312-317 pm Mg-Mg). Similar structural motifs occur in the compounds RE4IrMg, however, with a different connectivity of the building groups. The crystal chemistry of both structure types is comparatively discussed.< Leer menos