New Indium‐Rich Compounds EuRhIn2 and EuRh2In8

EuRhIn₂ and EuRh₂In₈ were obtained by reacting the elements in sealed tantalum 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, a = 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 variables for EuRh₂In₈. EuRhIn₂ adopts the MgCuAl₂ type structure and may be considered as a rhodium filled variant of the binary Zintl phase EuIn₂. The indium substructure is homeotypic to the lonsdaleite type. Within the three‐dimensional RhIn₂] polyanion the strongest bonding interactions occur for the Rh–In contacts followed by In–In. EuRh₂In₈ is the first indide with CaCo₂Al₈ type structure. The rhodium atoms have a trigonal prismatic indium coordination and the indium atoms form distorted indium centered InIn₈ cubes and InIn₁₀ pentagonal prisms with In–In distances ranging from 288 to 348 pm. Again, the rhodium and indium atoms together build a complex three‐dimensional Rh₂In₈] polyanion in which the europium atoms are located within distorted pentagonal channels. Chemical bonding in EuRhIn₂ and EuRh₂In₈ is briefly discussed.