SrIr9In18 - A Structurally Complex Intermetallic Compound with Sr@Ir4In12, Ir@In8 and Ir@In9 Building Units: SrIr9In18 - A Structurally Complex Intermetallic Compound with Sr@Ir4In12, Ir@In8 and Ir@In9 Building Units

Single crystals of SrIr9In18 were obtained by induction melting of the elements in a glassy carbon crucible followed by annealing at 1070 K. SrIr9In18 was structurally characterized by X-ray powder and single crystal diffraction: P (4) over bar m2, a = 811.21(5), c = 854.49(5) pm, wR(2) = 0.0511, 1223 F-2 values, and 46 variables. The structure is of a new type. The basic building units are Ir@In-8 (distorted square-prismatic, square anti-prismatic and bicapped trigonal prismatic coordination) and Ir@In-9 (distorted trigonal prismatic coordination) polyhedra, which condense to a three-dimensional network, which leaves large cavities for the strontium cations, which are coordinated to four iridium and twelve indium atoms. The [Ir9In18](2-) polyanionic network is stabilized through Ir-In (267-290 pm) and In-In (302-354 pm) bonding.