Eu3Co2In15 and KM2In9 (M = Co, Ni): 3D Frameworks Based on Transition Metal Centered In9 Clusters

Abstract

The title three compounds have been synthesized by solid state reactions at high temperatures, with excess indium as flux, and structurally characterized by single-crystal X-ray diffraction studies. Eu(3)Co(2)In(15) forms a new structure type and crystallizes in the tetragonal space group P4/mbm (No. 127), whereas KM(2)In(9) (M = Co, Ni) in the BaFe(2)Al(9) type crystallizes in the hexagonal space group P6/mmm (No. 191). Their structures all feature a three-dimensional anionic framework based on 1D [MIn(6)] single cluster chains composed of face-sharing [MIn(9)] clusters. In Eu(3)Co(2)In(15), two adjacent [CoIn(6)] single cluster chains form a [Co(2)In(11)] double cluster chain via corner-sharing In atoms as well as In-In bonds; the latter chains are further interconnected by additional indium atoms via In-In bonds into a complicated 3D framework, forming two types of tunnels along the c-axis, which are filled by the europium atoms. In KM(2)In(9), the [MIn(6)] single cluster chains are directly interconnected via corner sharing and exo In-In bonds into a 3D framework with the K(+) ions encapsulated in the 1D tunnels along the c-axis. Band structure calculations of three compounds based on density functional theory methods indicate that all three compounds are metallic.