Synthesis and Structure of Ca₁₈Li₅In_25.07:  A Novel Intergrowth of Li-Centered In₁₂ Icosahedral Clusters and Electron-Precise Zintl Layers

Abstract

A new ternary polar intermetallic, Ca(18)Li(5)In(25.07), was obtained from high-temperature reactions of the elements in welded Nb tubes. Its crystal structure, established by single-crystal X-ray diffraction, was found to crystallize in the orthorhombic space group Cmmm (No. 65). Unit cell parameters are a = 9.9151(6) A, b = 26.432(2) A, and c = 10.2116(6) A; Z = 2. The structure of Ca(18)Li(5)In(25.07) features two distinct types of indium anionic layers. An "electron-deficient" layer is made up of Li-centered In(12) icosahedra that are interconnected by bridging planar In(4) units and In atoms. A second In(3)(5-) layer is an electron-precise Zintl layer formed by fused four-, five-, and six-membered rings of three- and four-bonded indium atoms. The two distinct layers are alternately stacked and linked into a complex three-dimensional network. Vacancies are observed to occur only at the In(12) icosahedral and the bridging indium units within the "electron-deficient" layers. Magnetic property measurements indicate that Ca(18)Li(5)In(25.07) exhibits temperature-independent paramagnetism consistent with metallic behavior. Band structure calculations were performed to elucidate the role of defects and vacancies in the electronic structure of the electron-deficient "metallic" Zintl phase.

Novel Corrugated In9 Anionic Layer in Li2Y5In9: Square Pyramidal In5 Clusters Interconnected by Unusual Butterfly In4 Clusters

“…The In(2)−In(4) distance of 3.203(1) Å is slightly shorter than the In(4)−In(4) bonds. These In−In bonds are significantly longer than that of the Pauling single bond (∼2.96 Å) but are comparable to those reported in other indium phases. − The nearest In−In distance between neighboring In 5 cluster units is 3.985 (1) Å, which is much longer than those in La 3 In 5 and Y 3 In 5 . It should be mentioned that the square pyramidal In 5 units in La 3 In 5 ( C 2 v ) , α-Y 3 In 5 ( C s ), and β-Y 3 In 5 ( C 2 v ) are distorted and have a lower symmetry .…”

“…Some examples of mixed-cation indium phases are K 14 Na 20 In 96.30 in which two In 28 clusters are linked by two In atoms into a (In 28 )In 2 (In 28 ) sandwich unit, 20 A 3 Na 26 In 48 (A ) K, Rb, Cs) with a novel cubic network of arachno-and closo-In 12 , 21,22 K 18.2 Na 4.8 In 39 containing closo-In 12 plus an In 15 spacer in K 18.2 Na 4.8 In 39 , 23 and KNa 3 In 9 composed of closo-In 12 clusters plus four-bonded In atoms. 24 Two examples in which the two types of cations have different charges are Ca 18 Li 5 In 25.07 , featuring the intergrowth of defect cluster layers of Li-centered In 12 icosahedra (8-exo-bonds) with electron-precising In 3 5-Zintl layers, 25 and K 2 SrIn 7 with a remarkable electron-deficient indium network. 26 It is hoped that the combination of the alkali metal (A), such as lithium, and the rare earth (RE) metal, such as yttrium, which are different in both size and charge, can lead to novel ternary indium phases with unusual indium anionic clusters or networks.…”

The crystal structure and magnetic properties of a Zintl phase EuIrIn4: the first member of the Eu–Ir–In family

“…is capable of forming extensive polyanionic clusters, which renders structural diversity in these classes of compounds. Binary and pseudo-binary intermetallic Zintl phases containing indium and alkali/alkaline/rare earth (RE) metals as active components are highly studied for their structural diversity with different geometries ranging from zigzag chains, 1 layered icosahedra 2 to square pyramidal clusters, 3 pentagonal dodecahedra 4 and many other variations in novel bonding 5 and physical characteristics. 6,7 In some cases, these compounds have been classified as classical Zintl phases.…”

20 New compounds and structures in the solid state

“…Magnetic property measurements indicate that Ca 18 Li 5 In 25.07 exhibits temperature-independent paramagnetism consistent with metallic behaviour. 186 A new compound Ce 12 Pt 7 In was synthesised and its crystal structure is a fully ordered ternary derivative of the Gd 3 Ga 2 structure. Isostructural compounds have been formed with Pr, Nd and Ho.…”