Stella Quadrangula Research Articles

Renaissance of the Stella Quadrangula: The Lanthanoid Nitride Tellurides Ln13N5Te12 (Ln = La–Nd)

AbstractInvited for the cover of this issue is the group of Thomas Schleid from the University of Stuttgart, Germany. The cover image shows how both cationic components [N2Ln6]12+ and [N3Ln7]12+ in the title compounds Ln13N5Te12 (Ln = La–Nd) derive from a hypothetic stella quadrangula [N4Ln8]12+ of four edge‐sharing [NLn4]9+ tetrahedra by removal of the appropriate number of LnN equivalents.

Renaissance of the Stella Quadrangula: The Lanthanoid Nitride Tellurides Ln13N5Te12 (Ln = La–Nd)

Ln13N5Te12 (Ln = La–Nd), a quite unusual composition of the lanthanoid(III) nitride tellurides, appears with a new crystal structure and can be obtained by reactions of lanthanoid metal (Ln) with elemental tellurium (Te), sodium azide (NaN3), elemental iodine (I2) and sodium iodide (NaI) as flux in evacuated fused silica tubes for seven days at 900 °C. The black, shard‐shaped single crystals of the short new series Ln13N5Te12 (Ln = La–Nd) crystallize monoclinically in the space group P21/m with lattice parameters ranging from a = 1039.86(7), b = 1373.29(9), c = 1311.78(9) pm, β = 100.103(3)° for La13N5Te12 to a = 1016.73(7), b = 1337.58(9), c = 1288.92(9) pm, β = 100.094(3)° for Nd13N5Te12 and Z = 2. Unlike the other ternary compounds of the lanthanoid(III) nitride tellurides, two different types of isolated oligomers containing edge‐sharing [NLn4]9+ tetrahedra occur in their crystal structure. The fusion of two [NLn4]9+ units via one common edge forms [N2Ln6]12+ bitetrahedra, which are already known from the Ln3NTe3 examples with Ln = Gd–Ho. In contrast, the [N3Ln7]12+ trimers built up by three [NLn4]9+ tetrahedra with two sharing edges for each [NLn4]9+ unit, but three common edges overall, represent a new highlight. Both kinds of oligomers can be traced back to a stella quadrangula [N4Ln8]12+ and are embedded in a dense matrix of Te2– anions according to {[Ln6N2][Ln7N3]Te12}.

Vacancy ordering in Pd11Bi2Se2 - Crystal structure and properties

The crystal structure of Pd11Bi2Se2 was determined and refined from X-ray single crystal data (space group Fd3¯m, a = 12.4879(14) Å, Z = 8). In contrast to the earlier reported Pd3(Bi0.6Se0.4), the title compound crystallizes in a 2 × 2 × 2 superstructure of the BiF3 type with ordered bismuth and selenium distribution and an ordered vacancy according to Pd11□Bi2Se2. The vacancy is located at the center of a palladium tetrahedron capped with a bismuth tetrahedron (stella quadrangula). Pd11Bi2Se2 is isopointal to Li13In3 but shows different ordering of the minority components. Pd11Bi2Se2 is inert to water, organic solvents and concentrated hydrochloric acid and its melting point is 905(1) K. It exhibits a very small effective magnetic moment of μeff = 0.0114(2) μB per palladium atom. Pd11Bi2Se2 does not take up hydrogen up to 7.2(2) MPa hydrogen pressure and temperatures up to 703 K. In the electronic structure, the region near the Fermi level is dominated by almost filled Pd 4d-states. Low yet non-zero density of states and a pseudo-gap at the Fermi level might indicate Pd11Bi2Se2 to be a poor metal.

Synthesis, Characterization, and Chemical Bonding Analysis of the Lithium Alkaline‐earth Metal Gallide Nitrides Li2(Ca3N)2[Ga4] and Li2(Sr3N)2[Ga4

Large single crystals of Li2(Ca3N)2[Ga4] and Li2(Sr3N)2[Ga4] up to several mm in size were grown from mixtures of the respective elements and binary alkaline‐earth metal nitrides in reactive lithium melts employing a modified high‐temperature centrifugation‐aided filtration (HTCAF) technique. The main structural features of these isotypic phases are stella quadrangula building units [Ga4]Li4/2 and octahedra (Nae6/2), which form two independent interpenetrating networks. The phases crystallize in the η‐carbide structure and represent diamagnetic small bandgap semiconductors. Real‐space chemical bonding analysis indicates predominantly ionic bonding.

Synthesis and crystal structure of new K and Rb selenido/tellurido ferrate cluster compounds

Abstract In the course of a systematic study of alkali iron chalcogenido salts containing clusters [Fe4 Q 8] a series of new mixed-valent potassium and rubidium selenido and tellurido ferrates(II/III) was synthesized by carefully heating the pure elements enclosed in sample tubes under an argon atmosphere up to maximum temperatures of 800–900 °C. Their crystal structures have been determined by means of single crystal X-ray diffraction. The mixed-valent FeII/III tellurido ferrates A 7[Fe4Te8] form three different structure types. All structures contain tetramers of four edge sharing [FeTe4] tetrahedra, which are connected by common edges to form only slightly distorted tetrahedral [Fe4Te8]7− anions (‘stella quadrangula’) with a [Fe4Te4] cubane core. In all cases, these anions are surrounded by 26 alkali cations, which are located at the eight corners and the midpoints of the six faces and 12 edges of a cube. The three crystal structures can thus be described by three different packings of cuboid moieties: The monoclinic rubidium compound Rb7[Fe4Te8] (space group C2/c, a = 2000.16(7), b = 897.79(3), c = 1768.12(6) pm, β = 117.4995(10)°, Z = 4, R1 = 0.0296) is isotypic to the known cesium tellurido and sulfido ferrates Cs7[Fe4(S/Te)8]. Depending on the temperature, K7[Fe4Te8] forms two different but closely related new structure types: The tetragonal r.t. modification (space group P42/nmc, a = 1222.25(14), c = 872.1(2) pm, Z = 2, R1 = 0.0583) crystallizes in a supergroup of the orthorhombic l.t. (100 K) form (space group Pbcn, a = 1715.5, b = 866.76(3), c = 1715.50(7) pm, Z = 4, R1 = 0.0160). In all structures, the cluster centered cubes are stacked to form columns along the short (≈870 pm) axis. These columns are themselves densely packed with 4 (both K compounds) and 6 (A = Rb) adjacent face-sharing columns. According to these arrangements of cluster-centered cubes, a relation of the packing of K/Rb cations and cluster anions with the simple cubic packing can be established applying the crystallographic group-subgroup formalism. Attempts to synthesize the corresponding selenium compound K7[Fe4Se8] resulted in the formation of the likewise mixed-valent compound K6[Fe4Se8]. Despite the modified composition, the new orthorhombic structure (space group Pbcn, a = 1632.62(6), b = 821.10(3), c = 1592.75(6) pm, Z = 4, R1 = 0.0540) is almost isotypic to the l.t. form of K7[Fe4Te8], the only difference being a missing K site. K5Fe2Te5 crystallizes in a new structure type (cubic, space group Pa3̅, a = 1709.02(5) pm, Z = 4, R1 = 0.0594). According to K5Fe2Te5=K15[Fe3Te7]2(Te), its structure contains mixed-valent cuboidal trimers [Fe3Te7](6/7)− and isolated telluride ions, which are coordinated by cubes of K+ cations.

Magnetic-field-induced magnetism and thermal stability of carbides Fe6−xMoxC in molybdenum-containing steels

A hybrid method combining first-principles calculations and Weiss molecular field theory with thermodynamic data has been implemented to explore the origin of magnetic-field-induced precipitation behaviors for alloy carbides. The paramagnetic Mo atom disturbed the order of magnetic moment and resulted in a decrease in the Curie temperature for alloy carbide Fe6−xMoxC. The temperature dependence of magnetic moment and saturation magnetization of Fe atoms at different Wyckoff positions, as well as the saturation or induced magnetization of Fe6−xMoxC, decreased with increasing temperature. The higher Fe content and external magnetic field greatly increased the magnetization of alloy carbides. Two kinds of stella quadrangula lattices were employed to account for the total magnetism which was derived from the contribution of different Wyckoff sites of Fe atoms and Fe–C distances. The calculated total free energy taking into account magnetic field, temperature and composition was sufficient to provide quantitative agreement with experiment. The investigation of the effects of external field on the carbide precipitation behaviors led to a better understanding of the magnetic-field-induced phase transformation mechanism in heat resistant steels.

ChemInform Abstract: Geometric Frustration in Itinerant Electron Magnets

AbstractReview: 18 refs.

Neutron and X-ray diffraction studies on the high temperature phase of Mn3(VO4)2, the new isostructural compound NaMn4(VO4)3 and their mixed crystals NaxMn4.5−x/2(VO4)3 (0≤x≤1)

This paper presents a detailed structure analysis (combined Rietveld analysis of X-ray and neutron powder diffraction data as well as quantum mechanical calculations) of the high temperature phase of Mn3(VO4)2 (space group I4¯2d). Special attention is directed to the analysis of the local coordination around Mn2+ ions or vacancies within a stella quadrangula configuration of anions. Furthermore, the new compound NaMn4(VO4)3 is described as well as a range of mixed crystals between NaMn4(VO4)3 and Mn3(VO4)2 (described by the formula NaxMn4.5-x/2(VO4)3, 0≤x≤1) which were synthesized by a solid state route. All compounds were shown to be isostructural to the high temperature phase Mn3(VO4)2.

Geometric frustration in the stella quadrangula lattice and metamagnetism in Fe3Mo3N

η-carbide-type transition-metal compounds, which include the stella quadrangula lattice, are good candidates for testing the geometric frustration in the itinerant electron magnet. The broad peak observed in the temperature dependence of the susceptibility for one of the η-carbide-type bimetallic nitrides, Fe3Mo3N, has been confirmed microscopically by 95Mo NMR Knight-shift measurements. The itinerant electron metamagnetic transition observed in this compound is discussed in connection with the χ(T) behavior.

Copper(I) and silver(I) tertiary phosphines complexes: Synthesis, X-ray structures and spectroscopic characterization

Six new complexes, [Cu 4I 4(PPh 2Cy) 4]·2H 2O ( 1), [CuI(PPhCy 2) 2] ( 2), [CuCl(PPhCy 2) 2] ( 3), and [CuBr(PPh 3) 3]·CH 3CN ( 4), [Ag(PPhCy 2) 2(NO 3)] ( 5), [Ag(PCy 3)(NO 3)] 2 ( 6) [where Ph = phenyl, Cy = cyclohexyl], have been synthesized and structurally characterized by X-ray diffraction, IR absorption spectra and NMR spectroscopic studies (except complex 4). The X-ray diffraction analysis of complex ( 1), pseudo polymorph of complex [Cu 4I 4(PPh 2Cy) 4], reveals a stella quadrangula structure. The four corners of the cube are occupied by copper(I) atoms and four I atoms are present at the alternative corners of the cube, further more the copper(I) atoms are coordinated to a monodentate tertiary phosphine. Complexes ( 2) and ( 3) are isostructural with trigonal planar geometry around the copper(I) atom. The crystal structure of complex ( 4) is a pseudo polymorph of complex [CuBr(PPh 3) 3] and the geometrical environment around the copper(I) centre is distorted tetrahedral. In the Ag I complexes ( 5) and ( 6), the central metal atoms have pseudo tetrahedral and trigonal planar geometry, respectively. Spectroscopic and microanalysis results are consistent with the single crystal X-ray diffraction studies.

The Effect of Geometry on Electronic Properties of Transition Metal Compounds

The effect of geometry, particularly, geometric frustration on electronic properties of itinerant electron magnets are discussed. As an example, the competition between intra- and inter-dimer interaction, and the characteristic lattice dynamics in Mo3Sb7 are briefly reviewed. A new possible and promising candidate of the metallic frustrated lattice, the stella quadrangula lattice, found in compounds with the η-carbide type structure, etc., is introduced.

Self-assembly in tetrameric 1:1 silver(I) halide:tri- p-tolylphosphine complexes: An in-depth structural investigation

The reaction of silver(I) bromide with tri( p-tolyl)phosphine in MeCN solution in 1:1 molar ratios resulted in a complexes of the formula [AgBr{P(4-MeC 6H 4) 3}] 4. This compound has a tetrameric structure with a concave coordination polyhedron, in between a cube and a stella quadrangula. Weak silver–silver interactions were observed. The current compound is compared to the Cl and I analogs using distance–distance plots. The silver–silver interactions seem to dominate the geometry of these tetrameric type of complexes.

Polar binary Zn/Cd-rich intermetallics: Synthesis, crystal and electronic structure of A(Zn/Cd) 13 (A = alkali/alkaline earth) and Cs 1.34Zn 16

The binary alkali/alkaline earth (A) zinc and cadmium (M) compounds that form the NaZn 13 structure type (cubic, space group F m 3 ¯ c ), which were known only from indexed X-ray powder diagrams, have been synthesized from stoichiometric mixtures of the elements and have been structurally characterized using a combination of single crystal data and the Rietveld method. The alkali zinc phases A IZn 13 are only formed with the lighter alkali elements sodium to rubidium ( A I = Na : a = 1227.3(2) pm, R 1 = 0.0205 ; A I = K : a = 1237.9(3) pm, R 1 = 0.0154 ; A I = Rb : a = 1245.19(1) pm, R p = 0.0250 ), whereas the cadmium compounds A I Cd 13 are stable only for the heavier alkali metals potassium to cesium ( A I = K : a = 1379.2(4) pm, R 1 = 0.0118 ; A I = Rb : a = 1384.5(2) pm, R 1 = 0.0139 ; A I = Cs : a = 1392.0(3) pm, R 1 = 0.0381 ). In the crystal structures M-centered M(2)M(1) 12 icosahedra are connected via strong exobonds (forming tetrahedral stars, stella quadrangula) to form a 3D net, in the interstices of which the alkali metals are located in a snub cube 24 coordination. In contrast, the alkaline earth ( A II ) zinc compounds with calcium, strontium and barium ( A II = Ca : a = 1215.4(1) pm, R 1 = 0.0274 ; A II = Sr : a = 1222.2(2) pm, R 1 = 0.0154 ; A II = Ba : a = 1235.8(2) pm, R 1 = 0.0227 ) show statistical defects at the Zn(2) position centering the Zn(1) icosahedra. Both the geometric and the electronic stability of the NaZn 13 structure type, which can be assessed from the pseudo-bandgap calculated using FP-LAPW-DFT methods, are discussed. In contrast to the aforementioned systems, the NaZn 13 type ceases to exist in the binary system Cs–Zn. In this case a phase Cs 1.36Zn 16 with a new structure type but very similar stoichiometry emerges. This compound is the first and only known phase in the system Cs–Zn and crystallizes with a new incommensurably modulated structure: its average structure (orthorhombic, space group Imma, a = 264.2 ( 5 ) pm , b = 720.8 ( 14 ) pm , c = 1760 ( 5 ) pm, R 1 = 0.0198 ) already indicates the representative structural features: in a 3D net of Zn atoms tubular channels filled by the Cs atoms are formed. This Cs filling is, due to geometric requirements, not commensurate with the Zn host structure resulting in a modulated structure with satellite reflections that can be indexed with a q → vector of (0, 0, 0.2755). The final refinement in the superspace group ( P c n 2 ( 0 0 g ) s s o , a = 1760 ( 5 ) pm , b = 720.8 ( 14 ) pm , c = 264.2 ( 5 ) pm, w R main = 0.0550 , w R satellites = 0.140 ) shows a strong occupational and a weak positional modulation of Cs in the channels formed by the Zn partial structure.

On crystal chemistry of mercury chromates. Details of fragmentation and packing in crystal structures

In the crystal structures of the minerals edoylerite, deanesmithite, and wattersite and in the structures of the compounds HgCrO4, Hg3O2CrO4 (analog of the mineral schuetteite), and Pb2HgO2CrO4, there are atomic groups or fragments linked by relatively strong (covalent) bonds. The anion fragments represented by CrO4 tetrahedra are condensed into pairs and chains, in which adjacent tetrahedra are related by symmetry centers. The cation fragments form various patterns from zigzag ribbons of [Hg4S4] rings to ribbons and frameworks with [Hg6O2] r-octahedra, [Hg2CrO] and [Pb2HgO] triangles, and [Hg6Cr2O4] (stella quadrangula) groups. The symmetry of the fragments and their assemblies is analyzed. Analysis of the reference crystal-forming planes has revealed cation sublattices (close to the F-cubic sublattice in two cases), determining the typical features of the structures.

Synthese, cristallisation et determination structurale d'un compose de type scheelite dans le systeme lanthane-niobium-vanadium-oxygene

Synthesis and crystal growth of La(Nb 0.70V 0.30)O 4 with the scheelite type (CaWO 4) were performed by direct interaction of La 2O 3, Nb 2O 5, V 2O 5 oxides at 1640°C followed by a slow cooling down to the room temperature. La(Nb 0.70V 0.30)O 4 crystallizes in the tetragonal system, space group I4 1 a , with a = 5.3283(4) A ̊ , c = 11.717(2) A ̊ , V = 332.66(5) A ̊ 3 , Z = 4. The crystal structure has been refined to R = 0.031 using 324 independant hkl reflections and 15 variable parameters. This structure, isomorphous with LaNbO 4 high temperature form, exhibits statistical distribution of Nb 5+ and V 5+ in the tetrahedron of oxygens part of a stella quadrangula polyhedron. The La atom occupies a site coordinated to 8 oxygen atoms forming a bisdisphenoïd. The substitution of vanadium to niobium in LaNbO 4 stabilizes this high temperature form with the unusual tetrahedral coordination for niobium 5+.

A helical face-sharing tetrahedron chain from irrational twist, stella quadrangula, and related matters

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA helical face-sharing tetrahedron chain from irrational twist, stella quadrangula, and related mattersChong Zheng, Roald Hoffmann, and David R. NelsonCite this: J. Am. Chem. Soc. 1990, 112, 10, 3784–3791Publication Date (Print):May 1, 1990Publication History Published online1 May 2002Published inissue 1 May 1990https://doi.org/10.1021/ja00166a012RIGHTS & PERMISSIONSArticle Views289Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (810 KB) Get e-Alerts Get e-Alerts

ChemInform Abstract: The Structure of Silver(I) Iodide and Bromide, and the Silver(I) Solvate in Tetrahydrothiophene Solution: an X‐Ray Scattering and Raman Spectroscopic Study.

Abstract Structures of silver(I) iodide and bromide, and the solvated silver(I) ion are determined in tetrahydrothiophene solution with Large Angle X-ray Scattering (LAXS) technique. In a silver(I) perchlorate tetrahydrothiophene solution, silver(I) is solvated by four tetrahydrothiophene molecules in a regular tetrahedron. The main peak in the radial distribution function corresponds to four AgS distances at 2.526(7) A. An SS distance at 2.65(2) A in the solvent bulk is also included in the main peak. This shows that an internal structure exists in the tetrahydrothiophene bulk. Silver(I) iodide and bromide are tetrameric complexes with a stella quadrangula configuration, in saturated solution. The distances in the [AgI(SC4H8)]4 complex are AgI 2.799(4); AgAg, 3.072(6) and II, 4.638(19) A and in the [AgBr(SC4H8)]4 complex they are AgBr, 2.592(3); AgAg, 2.866(5) and BrBr, 4.25(4) A. The AgI bond distances in the [AgI(SC4H8)]4 complex is shorter in solution than in the solid solvate. This is because bulk tetrahydrothiophene is a markedly weaker donor than free tetrahydrothiophene due to the sulfursulfur interactions in the bulk, shown to be around 2.65 A. Raman spectroscopic studies on silver(I) and copper(I) iodide and silver(I) chloride tetrahydrothiophene solutions show that the polymetric structures predominate in concentrated solution and that they disintegrate upon dilution.

The structure of silver(I) iodide and bromide, and the silver(I) solvate in tetrahydrothiophene solution: An X-ray scattering and raman spectroscopic study

Structures of silver(I) iodide and bromide, and the solvated silver(I) ion are determined in tetrahydrothiophene solution with Large Angle X-ray Scattering (LAXS) technique. In a silver(I) perchlorate tetrahydrothiophene solution, silver(I) is solvated by four tetrahydrothiophene molecules in a regular tetrahedron. The main peak in the radial distribution function corresponds to four AgS distances at 2.526(7) Å. An SS distance at 2.65(2) Å in the solvent bulk is also included in the main peak. This shows that an internal structure exists in the tetrahydrothiophene bulk. Silver(I) iodide and bromide are tetrameric complexes with a stella quadrangula configuration, in saturated solution. The distances in the [AgI(SC 4H 8)] 4 complex are AgI 2.799(4); AgAg, 3.072(6) and II, 4.638(19) Å and in the [AgBr(SC 4H 8)] 4 complex they are AgBr, 2.592(3); AgAg, 2.866(5) and BrBr, 4.25(4) Å. The AgI bond distances in the [AgI(SC 4H 8)] 4 complex is shorter in solution than in the solid solvate. This is because bulk tetrahydrothiophene is a markedly weaker donor than free tetrahydrothiophene due to the sulfursulfur interactions in the bulk, shown to be around 2.65 Å. Raman spectroscopic studies on silver(I) and copper(I) iodide and silver(I) chloride tetrahydrothiophene solutions show that the polymetric structures predominate in concentrated solution and that they disintegrate upon dilution.

Darstellung und Kristallstrucktur von TlCu 3Te 2: Ein tellurocuprat mit aufgefülltem CuAl 2-typ

TlCu 3Te 2 is tetragonal, space group P4 2/ nnm with a = 8.427(4) A ̊ , c = 14.492(6) A ̊ , Z = 8. The structure was determined from four-circle diffractometer data and refined to a conventional R of 0.072 for 405 reflections with I > 3 σ( I). The crystal structure of TlCu 3Te 2 is of a new type. It is characterized by an anionic framework of copper-centred tellurium-tetrahedra. The Tl + ions are hosted in infinite channels running along [001]. They are coordinated to eight tellurium atoms in a distorted square antiprismatic configuration. The Tl-Te partial structure is related to the CuAl 2-structure type. The basic repetition unit of the tellurium packing can be described as a flattened stella quadrangula formed by four outer tetrahedra surrounding an inner tetrahedron. Along c the stellae quadrangulae are connected by common faces thus building up infinite columns. The columns share edges to form a three-dimensional framework wherein copper atoms alternatingly occupy the inner and outer tetrahedral sites.

Thestella quadrangulaas a structure building unit

In order to get a simple and accurate description of complex crystal structures, the stella quadrangula is used as a building unit to describe the following structures: SiF4, scheelite, NaZn13, Ru7B3 and Ba3Fe3Se7.