Grown from lithium flux,the ErCo5Si3.17 silicide is a combination of disordered derivatives of the UCo5Si3 and Yb6Co30P19 structure types

A ternary hexaerbium triacontacobalt enneakaidecasilicide, ErCo₅Si_3.17, crystallizes as a combination of disordered variants of the hexagonal UCo₅Si₃ (P6₃/m) and Yb₆Co₃₀P₁₉ (P) structure types and is closely related to the Sc₆Co₃₀Si₁₉ and Ce₆Rh₃₀Si₁₉ types. The Er, Co and three of the Si atoms occupy sites of m.. symmetry and a fourth Si atom occupies a site of .. symmetry. The environment of the Er atom is a 21‐vertex pseudo‐Frank–Kasper polyhedron. Trigonal prismatic coordination is observed for the Si atoms. The Co atoms are enclosed in heavily deformed cuboctahedra and 11‐vertex polyhedra. Crystallochemistry analysis and the data from electronic structure calculations (TB–LMTO–ASA) suggest that the Er atoms form positively charged cations which compensate the negative charge of the [Co₁₂Si₉]^m− polyanions.     

Crystal and electronic structures of La2LiGe6−x (x = 0.21) and La2LiGe4Si2

The synthesis and characterization of a new ternary dilanthanum lithium hexagermanide, La₂LiGe_6−x (x = 0.21), belonging to the Pr₂LiGe₆ structure type, and a quaternary dilanthanum lithium tetragermanium disilicide, La₂LiGe₄Si₂, which crystallizes as an ordered variant of this type, are reported. In both structures, Li is on a site of mmm symmetry. All other atoms are on sites of m2m symmetry. These structures are new representatives of a homologous linear structure series based on structural fragments of the AlB₂, CaF₂ and ZrSi₂ structure types. The observed 17‐vertex polyhedra are typical for La atoms and the environment of the Li atom is cubic. Two Ge atoms are enclosed in a tetragonal prism with one added atom (nine‐vertex polyhedron). The trigonal prismatic coordination is typical for Ge or Si atoms. The metallic nature of the bonding is indicated by the interatomic distances and electronic structure calculations.     

Li9Al4Sn5 as a new ordered superstructure of the Li13Sn5 type

Alloys from the ternary Li–Al–Sn system have been investigated with respect to possible applications as negative electrode materials in Li‐ion batteries. This led to the discovery of a new ternary compound, a superstructure of the Li₁₃Sn₅ binary compound. The ternary stannide, Li₉Al₄Sn₅ (nonalithium tetraaluminium pentastannide; trigonal, P m 1, hP18 ), crystallizes as a new structure type, which is an ordered variant of the binary Li₁₃Sn₅ structure type. One Li and one Sn site have m . symmetry, and all other atoms occupy sites of 3m . symmetry. The polyhedra around all types of atoms are rhombic dodecahedra. The electronic structure was calculated by the tight‐binding linear muffin‐tin orbital atomic spheres approximation method. The electron concentration is higher around the Sn and Al atoms, which form an [Al₄Sn₅]^m− polyanion.     

Li2Sn(OH)6

Hydro­thermally prepared dilithium tin hexa­hydro­xide crystallizes in the monoclinic system (space group P2₁/n), with the Sn atom at a site with symmetry and all other atoms in general positions. The Sn coordination polyhedron is made up of six hydro­xide groups. The Li atom is tetrahedrally coordinated by oxy­gen, with the tetrahedra sharing two corners and one edge with the adjacent Sn octahedra. Hydro­gen bonds between the OH groups provide additional bonds in the framework.     

A new tetragonal structure type for Li2B2C

The ternary dilithium diboron carbide, Li₂B₂C (tetragonal, space group Pm2, tP10), crystallizes as a new structure type and consists of structural fragments which are typical for structures of elemental lithium and boron or binary borocarbide B₁₃C₂. The symmetries of the occupied sites are .m. and 2mm. for the B and C atoms, and m2 and 2mm. for the Li atoms. The coordination polyhedra around the Li atoms are cuboctahedra and 15‐vertex distorted pseudo‐Frank–Kasper polyhedra. The environment of the B atom is a ten‐vertex polyhedron. The nearest neighbours of the C atom are two B atoms, and this group is surrounded by a deformed cuboctahedron with one centred lateral facet. Electronic structure calculations using the TB–LMTO–ASA method reveal strong B...C and B...B interactions.     

The Ce2Li0.39Ni1.61Si2 structure as a new derivative of the AlB2 family

A new quaternary dicerium lithium/nickel disilicide, Ce₂Li_0.39Ni_1.61Si₂, crystallizes as a new structure type of intermetallic compounds closely related to the AlB₂ family. The crystal–chemical interrelationships between parent AlB₂‐type, BaLiSi, ZrBeSi and the title compound are discussed using the Bärnighausen formalism. Two Ce atoms occupy sites of 3m. symmetry. The remainder, i.e. Ni, mixed Ni/Li and Si atoms, occupy sites of m2 symmetry. The environment of the Ce atom is an 18‐vertex polyhedron and the Ni, Ni/Li and Si atoms are enclosed in tricapped trigonal prisms. The title structure can be assigned to class No. 10 (trigonal prism and its derivatives) according to the Krypyakevich classification scheme [Krypyakevich (1977). In Structure Types of Intermetallic Compounds. Moscow: Nauka]. The electronic structure of the title compound was calculated using the tight‐binding linear muffin‐tin orbital method in the atomic spheres approximation (TB‐LMTO‐ASA). Metallic bonding is dominant in this compound. The strongest interactions are Ni—Si and Ce—Si.     

Tetrapotassium nonastannide,K4Sn9

In K₄Sn₉, which crystallizes with a new structure type, the Sn atoms form isolated Wade nido‐[Sn₉]^4? clusters of approxi­mate C_4v symmetry (monocapped square antiprisms), with Sn—Sn distances ranging from 2.9264 (9) to 3.348 (1) Å. The cluster anions are separated by K⁺ cations and are in a hexagonal close‐packed arrangement.     

A tetragonal polymorph of caesium hydroxide monohydrate,CsOH·H2O,from X‐ray powder data

Tetragonal caesium hydro­xide monohydrate, CsOH·H₂O, a clathrate hydrate, is a polymorph of three known hexagonal or pseudo‐hexagonal modifications. It was obtained as a by‐product in a high‐pressure experiment. Whether it is a high‐pressure polymorph, however, remains to be verified. The Cs atoms are situated in cavities of the form of a bicapped pentagonal prism, within an infinite three‐dimensional hydrogen‐bonded oxy­gen framework that is locally identical to layers found in the hexagonal modifications. The Cs atom and one of the two H atoms are at sites with symmetry, the O atom has mm site symmetry and the second H atom has 2/m symmetry.     

Li4Ge2B as a new derivative of the Mo2B5 and Li5Sn2 structure types

Binary and multicomponent intermetallic compounds based on lithium and p‐elements of Groups III–V of the Periodic Table are useful as modern electrode materials in lithium‐ion batteries. However, the interactions between the components in the Li–Ge–B ternary system have not been reported. The structure of tetralithium digermanium boride, Li₄Ge₂B, exhibits a new structure type, in the noncentrosymmetric space group R3m, in which all the Li, Ge and B atoms occupy sites with 3m symmetry. The title structure is closely related to the Mo₂B₅ and Li₅Sn₂ structure types, which crystallize in the centrosymmetric space group Rm. All the atoms in the title structure are coordinated by rhombic dodecahedra (coordination number = 14), similar to the atoms in related structures. According to electronic structure calculations using the tight‐binding–linear muffin‐tin orbital–atomic spheres approximation (TB–LMTO–ASA) method, strong covalent Ge—Ge and Ge—B interactions were established.     

Ba[Co3(VO4)2(OH)2] with a regular Kagomé lattice

The new layered title compound, barium di‐μ‐hydroxido‐di‐μ‐vanadato‐tricobaltate(II), was prepared under low‐temperature hydrothermal conditions. Its crystal structure comprises Co²⁺ and O²⁻ ions in the Kagomé geometry. The octahedral Co₃O₆(OH)₂ Kagomé layers, made up of edge‐shared CoO₄(OH)₂ octahedra with Co on a site of 2/m symmetry, alternate along the c axis with barium vanadate heteropolyhedral layers, in which Ba is on a site of m symmetry and V is on a site of 3m symmetry. All three O atoms and the H atom also occupy special positions: two O atoms and the H atom are on sites with 3m symmetry and one O atom is on a site with m symmetry. Ba[Co₃(VO₄)₂(OH)₂] represents the first compound from the four‐component BaO–CoO–V₂O₅–H₂O system and its structure is topologically related to the minerals vesignieite, Ba[Cu₃(VO₄)₂(OH)₂], and bayldonite, Pb[Cu₃(AsO₄)₂(OH)₂].     

The Neat Ternary Solid K5−xCo1−xSn9 with Endohedral [Co@Sn9]5− Cluster Units: A Precursor for Soluble Intermetalloid [Co2@Sn17]5− Clusters

A new type of Zintl phase is presented that contains endohedrally filled clusters and that allows for the formation of intermetalloid clusters in solution by a one‐step synthesis. The intermetallic compound K_5?xCo_1?xSn₉ was obtained by the reaction of a preformed Co? Sn alloy with potassium and tin at high temperatures. The diamagnetic saltlike ternary phase contains discrete [Co@Sn₉]^5? clusters that are separated by K⁺ ions. The intermetallic compound K_5?xCo_1?xSn₉ readily and incongruently dissolves in ethylenediamine and in the presence of 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane (2.2.2‐crypt), thereby leading to the formation of crystalline [K([2.2.2]crypt)]₅[Co₂Sn₁₇]. The novel polyanion [Co₂Sn₁₇]^5? contains two Co‐filled Sn₉ clusters that share one vertex. Both compounds were characterized by single‐crystal X‐ray structure analysis. The diamagnetism of K_5?xCo_1?xSn₉ and the paramagnetism of [K([2.2.2]crypt)]₅[Co₂Sn₁₇] have been confirmed by superconducting quantum interference device (SQUID) and EPR measurements, respectively. Quantum chemical calculations reveal an endohedral Co^1? atom in an [Sn₉]^4? nido cluster for [Co@Sn₉]^5? and confirm the stability of the paramagnetic [Co₂Sn₁₇]^5? unit.     

SrSn3 – eine supraleitende Legierung mit freien Elektronenpaaren

SrSn₃ – a Superconducting Alloy with Non‐bonding Electron Pairs SrSn₃ was synthesized from the elements in a welded niobium ampoule. The crystal structure was determined from X‐ray single crystal data. Space group R3m, a = 6,940(2) Å, c = 33,01(1) Å, Z = 12, Pearson symbol hR48. SrSn₃ shows an ordered atomic distribution on four crystallographic sites. The structure is build up from two closed packed atom layers (Sn1/Sr1 and Sn2/Sr2) each with the composition Sr : Sn = 1 : 3 and with hexagonal symmetry of the Sr atoms. The Sn atoms are shifted with respect to the ideal positions of a closed packed layer in a way that Sn triangles, which are separated by Sr atoms, result. Translational symmetry along the c axis arises from a 12‐layer stacking sequence with hexagonal and cubic closest packing motives. Due to the layer sequence ABABCACABCBC… units of three face‐sharing Sn octahedra result (condensation through Sn2 atoms) which form the Sn partial structure. The octahedra chains run parallel to the c axis and are connected by exclusively vertex sharing Sn octahedra (Sn1 atoms). Temperature dependent susceptibility measurements reveal superconducting properties. LMTO band structure calculations verify the metallic behavior. An analysis of the density of states with the help of the electron localization function (ELF) shows, that two kinds of lone pairs occur in this intermetallic phase: non‐bonding electron pairs with the shape of a sp² orbital hybrid are located at the Sn2 atoms and lone pairs with p orbital character are located at Sn1 atoms. The role of lone pairs with respect to the superconducting property is discussed.     

Synthesis and Structure of the Bicyclic [Sn4Se11]6– Anion in Na6Sn4Se11 · 22 H2O

Na₆Sn₄Se₁₁ · 22 H₂O can be crystallised at –8 °C as yellow‐orange needles from the 1 : 2 H₂O/CH₃OH mother liquor of a superheated reaction mixture of NaOH(s), Sn and Se. The bicyclic [Sn₄Se₁₁]^6– anion exhibits crystallographic C₂ symmetry and is composed of corner‐bridged SnSe₄ tetrahedra. Two opposite tin atoms of an Sn₄Se₄ 8‐membered ring are linked by a common Se atom, thereby affording two 6‐membered boat‐shaped Sn₃Se₃ rings with a shared Sn–Se–Sn bridging unit. [Sn₄Se₁₁]^6– thus represents the immediate precursor of the well‐known adamantane‐like [Sn₄Se₁₀]^4– anion.     

Li15Al3Si6 (Li14.6Al3.4Si6), a compound displaying a heterographite‐like anionic framework

The title compound, lithium aluminium silicide (15/3/6), crystallizes in the hexagonal centrosymmetric space group P6₃/m. The three‐dimensional structure of this ternary compound may be depicted as two interpenetrating lattices, namely a graphite‐like Li₃Al₃Si₆ layer and a distorted diamond‐like lithium lattice. As is commonly found for LiAl alloys, the Li and Al atoms are found to share some crystallographic sites. The diamond‐like lattice is built up of Li cations, and the graphite‐like anionic layer is composed of Si, Al and Li atoms in which Si and Al are covalently bonded [Si—Al = 2.4672 (4) Å].     

Li12Cu16+xAl26−x (x = 3.2): a new intermetallic structure type

The new ternary lithium copper aluminide, Li₁₂Cu_16+xAl_26−x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li₁₂Cu_16+xAl_26−x consists of pseudo‐Frank–Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl₂ and Li₈Cu_12+xAl_6−x) and to the well known CaCu₅ structure.     

Endohedrally Filled [Ni@Sn9]4− and [Co@Sn9]5− Clusters in the Neat Solids Na12Ni1−xSn17 and K13−xCo1−xSn17: Crystal Structure and 119Sn Solid‐State NMR Spectroscopy

A systematic approach to the formation of endohedrally filled atom clusters by a high‐temperature route instead of the more frequent multistep syntheses in solution is presented. Zintl phases Na₁₂Ni_1?xSn₁₇ and K_13?xCo_1?xSn₁₇, containing endohedrally filled intermetalloid clusters [Ni@Sn₉]^4? or [Co@Sn₉]^5? beside [Sn₄]^4?, are obtained from high‐temperature reactions. The arrangement of [Ni@Sn₉]^4? or [Co@Sn₉]^5? and [Sn₄]^4? clusters, which are present in the ratio 1:2, can be regarded as a hierarchical replacement variant of the hexagonal Laves phase MgZn₂ on the Mg and Zn positions, respectively. The alkali‐metal positions are considered for the first time in the hierarchical relationship, which leads to a comprehensive topological parallel and a better understanding of the composition of these compounds. The positions of the alkali‐metal atoms in the title compounds are related to the known inclusion of hydrogen atoms in the voids of Laves phases. The inclusion of Co atoms in the {Sn₉} cages correlates strongly with the number of K vacancies in K_13?xCo_1?xSn₁₇ and K_5?xCo_1?xSn₉, and consequently, all compounds correspond to diamagnetic valence compounds. Owing to their diamagnetism, K_13?xCo_1?xSn₁₇, and K_5?xCo_1?xSn₉, as well as the d‐block metal free binary compounds K₁₂Sn₁₇ and K₄Sn₉, were characterized for the first time by ¹¹⁹Sn solid‐state NMR spectroscopy.     

Lanthanum tetrazinc,LaZn4

The structure of lanthanum tetrazinc, LaZn₄, has been determined from single‐crystal X‐ray diffraction data for the first time, approximately 70 years after its discovery. The compound exhibits a new structure type in the space group Cmcm, with one La atom and two Zn atoms occupying sites with m2m symmetry, and one Zn atom occupying a site with 2.. symmetry. The structure is closely related to the BaAl₄, La₃Al₁₁, BaNi₂Si₂ and CaCu₅ structure types, which can be presented as close‐packed arrangements of 18‐vertex clusters, in this case LaZn₁₈. The kindred structure types contain related 18‐vertex clusters around atoms of the rare earth or alkaline earth metal.     

Europium(II) oxy­iodide

Yellow single crystals of Eu₄OI₆ were grown from fluxes in Ta ampoules and structurally characterized by X‐ray diffraction. Eu₄OI₆ crystallizes in a hexagonal system and is isotypic with the corresponding chloride and bromide compounds. The O atom and one Eu atom lie on sites with 3m symmetry; the other Eu atom and the two unique I atoms are at sites with m symmetry. The structure is characterized by O‐centered tetrahedra of divalent europium cations [Eu—O = 2.391 (15) and 2.416 (5) Å, and mean Eu—Eu = 3.94 Å] and hexagonal channels along [001] filled with iodide anions.     

Dy2Ni7Sn3: a new member of the CaCu5 family of intermetallics

Single crystals of didysprosium heptanickel tritin were synthesized from the constituent elements by arc‐melting. Two of the five Ni atoms are at general sites and all other atoms are at sites with either twofold or m symmetry. The structure contains `DyNi<sub>5</sub>Sn' and `DyNi₂Sn₂' fragments and represents a new member of the CaCu₅ series of intermetallics.     

Ba3Li2V2O7Cl4, a new vanadate with a channel structure

The tribarium dilithium divanadate tetrachloride Ba₃Li₂V₂O₇Cl₄ is a new vanadate with a channel structure and the first known vanadate containing both Ba and Li atoms. The structure contains four non‐equivalent Ba²⁺ sites (two with m and two with 2/m site symmetry), two Li⁺ sites, two nonmagnetic V⁵⁺ sites, five O²⁻ sites (three with m site symmetry) and four Cl⁻ sites (m site symmetry). One type of Li atom lies in LiO₄ tetrahedra (m site symmetry) and shares corners with VO₄ tetrahedra to form eight‐tetrahedron Li₃V₅O₂₄ rings and six‐tetrahedron Li₂V₄O₁₈ rings; these rings are linked within porous layers parallel to the ab plane and contain Ba²⁺ and Cl⁻ ions. The other Li atoms are located on inversion centres and form isolated chains of face‐sharing LiCl₆ octahedra.