Lead-flux Growth of Eu4Ir8As7 Crystals

Single crystals of the new arsenide Eu₄Ir₈As₇ were grown from a lead flux. The structure was refined on the basis of single-crystal X-ray diffractometer data: Ca₄Ir₈P₇ type, P2₁/m, a = 1311.3(1), b = 408.4(1), c = 1360.3(1) pm, β =98.45(1)°, wR2 = 0.0640, 1985 F² values, 95 variables. The iridium and arsenic atoms in the Eu₄Ir₈As₇ structure build up a complex three-dimensional, covalently bonded [Ir₈As₇] network with Ir–As distances ranging from 239 to 260 pm. Each iridium atom has three or four arsenic neighbors in slightly distorted trigonal-planar or tetrahedral coordination. The four crystallographically independent europium atoms fill cavities of coordination numbers 12, 13, and 15 (2 ×) within the [Ir₈As₇] network. Parts of the Eu₄Ir₈As₇ structure resemble known simpler structure types, and one can describe the Eu₄Ir₈As₇ structure as an intergrowth variant of CaBe₂Ge₂-, TiNiSi- and AlB₂-related slabs.