On the silicides EuIr2Si2 and Lu5Si3

EuIr2Si2 was synthesized from the elements in a sealed tantalum tube in a water-cooled sample chamber of an induction furnace. Lu5Si3 was obtained by arc-melting of the elements. Both silicides were investigated by X-ray powder and single crystal diffraction: BaAl4 type, I4/mmm, a = 407.4(1), c = 1010.8(7) pm, wR2 = 0.0492, 134 F-2 values, 9 variables for EuIr2Si2 and Mn5Si3 type, P6(3)/mcm, a = 820.0(1), c = 614.2(1) pm, wR2 = 0.0511, 311 F-2 values and 12 variables for Lu5Si3. The iridium and silicon atoms in EuIr2Si2 build up a three-dimensional [Ir2Si2] network with Ir-Si and Si-Si interactions. The europium atoms fill cages within the network. The metal-rich silicide Lu5Si3 contains columns of face-sharing, empty Lu-6 octahedra and isolated silicon atoms in a distorted tri-capped trigonal prismatic coordination. Chemical bonding in these silicides is briefly discussed.