New indium-rich compounds EuRhIn2 and EuRh(2)In8

EuRhIn2 and EuRh2In8 were obtained by reacting the elements in sealed tanta lum tubes in a high-frequency furnace in a water-cooled quartz glass sample chamber. Both indides were investigated by X-ray powder and single crystal techniques: Cmcm, oC16, n = 432.2(1), b = 1058.8(1), c = 805.5(2)pm, wR2 = 0.0393, 471 F-2 values, 16 variables for EuRhIn2 and Pbam, oP44, a = 1611. 8(2), b = 1381.7(2), c = 436.44(6) pm, wR2 = 0.0515, 1592 F-2 values, 70 va riables for EnRh(2)In(8). EuRhIn2 adopts the MgCuAl2 type structure and may be considered as a rhodium filled variant of the binary Zint1 phase EuIn2. The indiurn substructure is homeotypic to the lonsdaleite type. Within the three-dimensional [RhIn2] polyanion the strongest bonding interactions occ ur for the Rh-In contacts followed by In-In. EuRhzIna is the first indide w ith CaCo2Al8 type structure. The rhodium atoms have a trigonal prismatic in dium coordination and the indium atoms form distorted indium centered InIn8 cubes and InIn10 pentagonal prisms with In-In distances ranging from 288 t o 348 pm. Again, the rhodium and indium atoms together build a complex thre e-dimensional [Rh2In8] polyanion in which the europium atoms are located wi thin distorted pentagonal channels. Chemical bonding in EuRhIn2 and EuRh2In 8 is briefly discussed.