Eu₂Ru₃Si₅ and Eu₂Ir₃Ga₅ – first europium compounds with U₂Mn₃Si₅-type structure but different europium valence

Abstract The silicide Eu 2 Ru 3 Si 5 was synthesized from the elements in a sealed tantalum tube in a high-frequency furnace, while the gallide Eu 2 Ir 3 Ga 5 was obtained by arc-melting. Both structures were refined from single-crystal X-ray diffractometer data: P 4/ mnc , a = 1072.69(8), c = 569.55(5) pm, wR = 0.0453, 617 F 2 values, 31 variables for Eu 2 Ru 3 Si 5 and a = 1122.18(7), c = 583.17(4) pm, wR = 0.0546, 729 F 2 values, 31 variables for Eu 2 Ir 3 Ga 4.95(1) . The gallide shows small defects on one 8 h site. The transition metal atoms in Eu 2 Ru 3 Si 5 and Eu 2 Ir 3 Ga 5 have octahedral p element coordination. These Ru@Si 6 respectively Ir@Ga 6 polyhedra are condensed to three-dimensional [Ru 3 Si 5 ] 6− respectively [Ir 3 Ga 5 ] 4− polyanionic networks. The ground states of Eu(III) in Eu 2 Ru 3 Si 5 and Eu(II) in Eu 2 Ir 3 Ga 5 were determined by 151 Eu Mössbauer spectroscopy.