Synthesis and structural characterization of the type‐I clathrates K8AlxSn46–x and Rb8AlxSn46–x (x ≃ 6.4–9.7)

Exploratory studies in the systems A–Al–Sn (A = K and Rb) yielded the clathrates K₈Al_xSn_46–x (potassium aluminium stannide) and Rb₈Al_xSn_46–x (rubidium aluminium stannide), both with the cubic type‐I structure (space group Pmn, No. 223; a ? 12.0 Å). The Al:Sn ratio is close to the idealized A₈Al₈Sn₃₈ composition and it is shown that it can be varied slightly, in the range of ca ±1.5, depending on the experimental conditions. Both the (Sn,Al)₂₀ and the (Sn,Al)₂₄ cages in the structure are fully occupied by the guest alkali metal atoms, i.e. K or Rb. The A₈Al₈Sn₃₈ formula has a valence electron count that obeys the valence rules and represents an intrinsic semiconductor, while the experimentally determined compositions A₈Al_8±xSn_38?x suggest the synthesized materials to be nearly charge‐balanced Zintl phases, i.e. they are likely to behave as heavily doped p‐ or n‐type semiconductors.     

Unravelling Local Atomic Order of the Anionic Sublattice in M(Al1−xGax)4 with M=Sr and Ba by Using NMR Spectroscopy and Quantum Mechanical Modelling

The quasibinary section of the intermetallic phases MAl₄ and MGa₄ with M=Sr and Ba have been characterised by means of X‐ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al_1?xGa_x)₄ with M=Sr and Ba. These structures crystallise in the BaAl₄ structure type with four‐ and five‐bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state ²⁷Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al_1?xGa_x)₄ with M=Sr and Ba and 0.925≤x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, ²⁷Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)–Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results.     

K and Ba distribution in the structures of the clathrate compounds KxBa16−x(Ga,Sn)136 (x = 0.8, 4.4, and 12.9) and KxBa8−x(Ga,Sn)46 (x = 0.3)

Studies of the K–Ba–Ga–Sn system produced the clathrate compounds K_0.8(2)Ba_15.2(2)Ga_31.0(5)Sn_105.0(5) [a = 17.0178 (4) Å], K_4.3(3)Ba_11.7(3)Ga_27.4(4)Sn_108.6(4) [a = 17.0709 (6) Å] and K_12.9(2)Ba_3.1(2)Ga_19.5(4)Sn_116.5(4) [a = 17.1946 (8) Å], with the type‐II structure (cubic, space group Fdm), and K_7.7(1)Ba_0.3(1)Ga_8.3(4)Sn_37.7(4) [a = 11.9447 (4) Å], with the type‐I structure (cubic, space group Pmn). For the type‐II structures, only the smaller (Ga,Sn)₂₄ pentagonal dodecahedral cages are filled, while the (Ga,Sn)₂₈ hexakaidecahedral cages remain empty. The unit‐cell volume is directly correlated with the K:Ba ratio, since an increasing amount of monovalent K occupying the cages causes a decreasing substitution of the smaller Ga in the framework. All three formulae have an electron count that is in good agreement with the Zintl–Klemm rules. For the type‐I compound, all framework sites are occupied by a mixture of Ga and Sn atoms, with Ga showing a preference for Wyckoff site 6c. The (Ga,Sn)₂₀ pentagonal dodecahedral cages are occupied by statistically disordered K and Ba atoms, while the (Ga,Sn)₂₄ tetrakaidecahedral cages encapsulate only K atoms. Large anisotropic displacement parameters for K in the latter cages suggest an off‐centering of the guest atoms.     

Binäre Lanthan‐Stannide mit Sn:La‐Verhältnissen nahe 1:1 – Synthesen,Kristallstrukturen, Chemische Bindung

Four binary lanthanum stannides close to the 1:1 ratio of Sn:La were synthesized from mixtures of the elements. The structures of the compounds have been determined by means of single‐crystal X‐ray data. The low temperature (α) form of LaSn (CrB‐type, orthorhombic, space group Cmcm, a = 476.33(6), b = 1191.1(2), c = 440.89(6) pm, Z = 4, R1 = 0.0247), crystallizes with the CrB‐type. The structure exhibits planar tin zigzag chains with a Sn–Sn bond length of 299.1 pm. In contrast to the electron precise Zintl compounds of the alkaline earth elements, additional La–Sn bonding contributions become apparent from the results of band structure calculations. In the somewhat tin‐richer region, the new compound La₃Sn₄ (orthorhombic, space group Cmcm, a = 451.45(4), b = 1190.44(9), c = 1583.8(2) pm, Z = 4, R1 = 0.0674), crystallizing with the Er₃Ge₄ structure type, exhibits Sn₃ segments of the zigzag chains of α‐LaSn together with a further Sn atom in a square planar Sn coordination with increased Sn–Sn bond lengths. In the Lanthanum‐richer region, La₁₁Sn₁₀ (tetragonal, space group I4/mmm, a = 1208.98(5), c = 1816.60(9) pm, Z = 4, R1 = 0.0325) forms the undistorted tetragonal Ho₁₁Ge₁₀ structure type. Its structure, which contains isolated Sn atoms, [Sn₂] dumbbells and planar [Sn₄] rings is related to the high temperature (β) form of LaSn. The structure of β‐LaSn (space group Cmmm, a = 1766.97(6), b = 1768.28(5), c = 1194.32(3) pm, Z = 60, R1 = 0.0453), which forms a singular structure type, can be derived from that of La₁₁Sn₁₀ by the removal of thin slabs. Due to the different stacking of the remaining layers, planar [Sn₄] chain segments and linear [Sn–Sn–Sn] anions are formed as additional structural elements. The chemical bonding (Sn–Sn covalent bonding, Sn–La contributions) is discussed on the basis of the simple Zintl concept and the results of FP‐LAPW calculations (density of states, band structure, valence electron densities and electron localization function).     

Transmetallierung von Zinn(II) in [Sn(μ3‐PSitBu3)]4 durch Barium – von Sn4P4‐Heterocuban‐Strukturen zu heterobinuklearen Käfigverbindungen mit einem zentralen BanSn4−nP4‐Heterocuban‐Polyeder (n = 1, 2 und 3)

Transmetallation of Tin(II) in [Sn(μ₃‐PSitBu₃)]₄ by Barium – from Sn₄P₄ Heterocubane Structures to Heterobinuclear Cage Compounds with a Central Ba_nSn_4?nP₄ Heterocubane Polyhedron (n = 1, 2 and 3) For the preparation of compounds of the type [Ba_nSn_4?n(PSitBu₃)₄] (n = 1 ( 2 ), 2 ( 3 ) and 3 ( 4 )) two synthetic routes are applicable: in the transmetallation reaction homometallic [Sn₄(PSitBu₃)₄] ( 1 ) reacts with barium metal and in a deprotonation reaction (metallation) tri(tert‐butyl)silylphosphane reacts simultaneously with (thf)₂Ba[N(SiMe₃)₂]₂ and Sn[N(SiMe₃)₂]₂. During the transmetallation reaction mixtures of the heterobimetallic cage compounds 2 to 4 are obtained, however, analytically pure compounds 2 and 3 are accessible by the metallation reaction. Compound 4 is formed as a minor product together with 3 . Due to the larger Ba‐P bond lengths compared to the Sn‐P values the substitution of tin by barium leads to strong distortions of the heterocubane moiety. With NMR‐spectroscopic experiments one could show that all the above mentioned compounds form Ba_nSn_4?nP₄ heterocubane cage structures.     

Tetrakis(μ2‐4‐aminobenzoato)di‐μ3‐oxido‐tetrakis[dibutyltin(IV)]

The molecule of the title compound, [Sn₄(C₄H₉)₈(C₇H₆NO₂)₄O₂], lies about an inversion centre and is a tetranuclear bis(tetrabutyldicarboxylatodistannoxane) complex containing a planar Sn₄O₂ core in which two μ₃‐oxide O atoms connect an Sn₂O₂ ring to two exocyclic Sn atoms. Each Sn atom has a highly distorted octahedral coordination. In the molecule, the carboxylate groups of two aminobenzoate ligands bridge the central and exocyclic Sn atoms, while two further aminobenzoate ligands have highly asymmetric bidentate chelation to the exocyclic Sn atoms plus long O...Sn interactions with the central Sn atoms. Each Sn atom is also coordinated by two pendant n‐butyl ligands, which extend roughly perpendicular to the plane of the Sn₄O₁₀ core. Only one of the four unique hydrogen‐bond donor sites is involved in a classic N—H...O hydrogen bond, and the resulting supramolecular hydrogen‐bonded structure is an extended two‐dimensional network which lies parallel to the (100) plane and consists of a checkerboard pattern of four‐connected molecular cores acting as nodes. The amine groups not involved in the hydrogen‐bonding interactions have significant N—H...π interactions with neighbouring aminobenzene rings.     

Al14Ba8La26.3Ru18Sr53.7O167: a variant of cubic perovskite with isolated RuO6 units

The crystal structure of the title aluminium barium lanthanum ruthenium strontium oxide has been solved and refined using neutron powder diffraction to establish the parameters of the oxygen sublattice and then single‐crystal X‐ray diffraction data for the final refinement. The structure is a cubic modification of the perovskite ABO₃ structure type. The refined composition is Ba_0.167La_0.548Sr_1.118Ru_0.377Al_0.290O_3.480, and with respect to the basic perovskite structure type it might be written as (Ba₈La_13.68Sr_34.32)(Al_13.92La_12.64Ru_18.08Sr_19.36)O_192−x, with x = 24.96. The metal atoms lie on special positions. The A‐type sites are occupied by Ba, La and Sr. The Ba atoms are located in a regular cuboctahedral environment, whereas the La and Sr atoms share the same positions with an irregular coordination of O atoms. The B‐type sites are divided between two different Wyckoff positions occupied by Ru/Al and La/Sr. Only Al and Ru occupy sites close to the ideal perovskite positions, while La and Sr move away from these positions toward the (111) planes with high Al content. The structure contains isolated RuO₆ octahedra, which form tetrahedral substructural units.     

ChemInform Abstract: The Crystal Structures of m,o‐Ce3Pt4Sn6 and Ce1‐xPt6Al13+2x.

Single crystals of Ce₃Pt₄Sn₆ (I) and Ce_1‐xPt₆Al_13+2x (x = 0.207, (II)) are isolated by mechanical fragmentation of specimens grown from self‐fluxes (Sn or Al, resp.) by slow cooling from the melt.     

Alkalimetall‐Stannid‐Silicate und ‐Germanate: ‘Doppelsalze’ mit dem Zintl‐Anion [Sn4]4—

Alkaline Metal Stannide‐Silicates and ‐Germanates: ‘Double Salts’ with the Zintl Anion [Sn₄]^4— The crystal structures of the tetrelid tetrelates A₁₂[Sn₄]₂[GeO₄] (A = Rb/Cs: monoclinic, P2₁/c, a = 1289.1(2) / 1331.72(7), b = 2310.1(4)/ 2393.6(1), c = 1312.6(2)/ 1349.21(7) pm, β = 119.007(3)/ 118.681(1)°, Z = 4, R1 = 0.1049/0.0803) and Cs₂₀[Sn₄]₂[SiO₄]₃ (monoclinic, Cc, a = 2331.9(1), b = 1340.1(2), c = 1838.9(2) pm, β= 102.61(3)°, R1 = 0.0763) contain the Zintl anions [Sn₄]^4— and isolated oxotetrelate ions [MO₄]^4— (M = Si, Ge). The high temperature form of CsSn crystallizes with the KGe type (cubic, P4¯3n, a = 1444.7(1) pm, R1 = 0.0395).     

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.     

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.     

Neue molekulare Indium‐Zinn‐Sauerstoff‐ und Indium‐Zinn‐Natrium‐Sauerstoff‐Chlor‐Cluster

Abstract. The five‐membered heteroelement cluster THF · Cl₂In(O^tBu)₃Sn reacts with the sodium stannate [Na(O^tBu)₃Sn]₂ to produce either the new oxo‐centered alkoxo cluster ClInO[Sn(O^tBu)₂]₃ ( 1 ) (in low yield) or the heteroleptic alkoxo cluster Sn(O^tBu)₃InCl₃Na[Sn(O^tBu)₂]₂ ( 2 ). X‐ray diffraction analyses reveal that in compound 1 the polycyclic entity is made of three tin atoms which together with a central oxygen atom form a trigonal, almost planar triangle, perpendicular to which a further indium atom is connected through the oxygen atom. The metal atoms thus are arranged in a Sn₃In pyramid, the edges of which are all saturated by bridging tert‐butoxy groups. The indium atom has a further chloride ligand. Compound 2 has two trigonal bipyramids as building blocks which are fused together at a six coordinate indium atom. One of the bipyramids is of the type SnO₃In with tert‐butyl groups on the oxygen atoms, while the other has the composition InCl₃Na with chlorine atoms connecting the two metals. The sodium atom in 2 has further contacts to two plus one alkoxide groups which are part of a[Sn(O^tBu)₂]₂ dimer disposing of a Sn₂O₂ central cycle. The hetero element cluster in 2 thus combines three closed entities and its skeleton SnO₃InCl₃NaO₂Sn₂O₂ consists of three different metallic and two different non‐metallic elements.     

Die Aluminidiodide La24Al12I21 und La10Al5I8: Verbindungen mit intermetallischen La‐Al‐Bereichen und La‐Al‐Clustern

The Aluminide Iodides La₂₄Al₁₂I₂₁ and La₁₀Al₅I₈: Compounds with Intermetallic La‐Al Fractions and La‐Al Clusters Reacting pieces of La, LaI₃ and Al filings (molar ratio 22 : 8 : 15) at 800 °C–825 °C results in La₂₄Al₁₂I₂₁ (70 % yield) together with La₁₀Al₅I₈ (10 % yield), besides known La₃Al₂I₂ and La₂Al₂I. Both new compounds form golden coloured needles. La₁₀Al₅I₈ is brittle, whereas La₂₄Al₁₂I₂₁ is shaped as hair‐like easily deformable bundles. Both are monoclinic, space group C2/m, La₂₄Al₁₂I₂₁ with a = 35.753(7) Å, b = 4.327(1) Å, c = 27.442(6) Å, β = 116.62(3)° and La₁₀Al₅I₈ with a = 19.649(1) Å, b = 4.296(1) Å, c = 18.0290(1) Å and β = 96.67(3)°. The La atoms form trigonal prisms condensed into double chains along [010]. The La prisms are centered by Al atoms which form Al₆ rings connected into chains. The La‐Al strands are surrounded by I atoms in La₂₄Al₁₂I₂₁, whereas in La₁₀Al₅I₈ they are connected to form corrugated sheets separated by close packed layers of I atoms together with Al atoms. The octahedral voids around the Al atoms are occupied by La atoms, and such La₆Al clusters are connected via opposite edges to octahedra chains along [010].     

The Sialons MLn[Si4−xAlxOxN7−x] with M = Eu,Sr, Ba and Ln = Ho‐Yb – Twelve Substitution Variants with the MYb[Si4N7] Structure Type

The oxonitridoalumosilicates (so‐called sialons) MLn[Si_4?xAl_xO_xN_7?x] with M = Eu, Sr, Ba and Ln =Ho, Er, Tm, Yb were obtained by the reaction of the respective lanthanoid metal, the alkaline earth carbonates or europium carbonate, resp., AlN, “Si(NH)₂” and MCl₂ as a flux in a radiofrequency furnace at temperatures around 2100 °C. The compounds MLn[Si_4?xAl_xO_xN_7?x] are relevant for the investigation of substitutional effects on the materials properties due to their ability of tolerating a comparatively large phase width up to x ≈ 2.0(5). The crystal structures of the twelve compounds were refined from X‐ray single crystal data and X‐ray powder data and are found to be isotypic to the MYb[Si₄N₇] structure type. The compounds crystallize in space group P6₃mc (no. 186, hexagonal) and are made up of chains of so‐called starlike units [N^[4](SiN₃)₄] or [N^[4]((Si,Al)(O,N)₃)₄], respectively. These units are formed by four (Si,Al)(N/O)₄ tetrahedra sharing a common central nitrogen atom. The structure refinement was performed utilizing an O/N‐distribution model according to Paulings rules, i.e. nitrogen was positioned on the four‐fold bridging site and nitrogen and oxygen were distributed equally on both of the two‐fold bridging sites, resulting in charge neutrality of the compound. The Si and Al atoms were distributed equally on their two crystallographic sites, referring to their elemental proportion in the compound, due to being poorly distinguishable by X‐ray methods. The chemical compositions of the compounds were derived from electron probe micro analyses (EPMA).     

Chloro­di­methyl(N‐methyl­pyrrolidin­one)­tin(IV)‐μ‐chloro‐di­chloro­di­methyl­tin(IV)

The synthesis and the X‐ray structural analysis of the title compound, μ‐chloro‐1:2κ²Cl‐tri­chloro‐1κCl,2κ²Cl‐tetra­methyl‐1κ²C,2κ²C‐(N‐methyl­pyrrolidin‐2‐one)‐1κO‐ditin(IV), [Sn₂Cl₄(CH₃)₄(C₅H₉NO)], are described. The title compound is found to exhibit a distorted trigonal–bipyramidal geometry at both Sn^IV atoms. The Sn—Cl—Sn angle involving the bridging chlorine ligand is 135.56 (5)°, with the Sn—Cl bond lengths being 2.5704 (13) and 3.1159 (13) Å.     

A2SnS5: A Structural Incommensurate Modulation Exhibiting Strong Second‐Harmonic Generation and a High Laser‐Induced Damage Threshold (A=Ba,Sr)

Structural modulations have been recently found to cause some unusual physical properties, such as superconductivity or charge density waves; however, thus‐induced nonlinear optical properties are rare. We report herein two unprecedented incommensurately modulated nonlinear optical sulfides exhibiting phase matching behavior, A₂SnS₅ (A=Ba, Sr), with the (3+1)D superspace groups P2₁2₁2(00γ)00s or P2₁(α0γ)0, featuring different modulations of the [Sn₂S₇]_∞ belts. Remarkably, Ba₂SnS₅ exhibits an excellent second harmonic generation (SHG) of 1.1 times that of the benchmark compound AgGaS₂ at 1570 nm and a very large laser‐induced damage threshold (LIDT) of 8×AgGaS₂. Theoretical studies revealed that the structural modulations increase the distortions of the Sn/S building units by about 44 or 25 % in A₂SnS₅ (A=Ba, Sr), respectively, and enhance significantly the SHG compared with α‐Ba₂SnSe₅ without modulation. Besides, despite the smaller E_g, the A₂SnS₅ samples exhibit higher LIDTs owing to their smaller thermal expansion anisotropies (Ba₂SnS₅ (1.51)<Sr₂SnS₅ (2.08)<AgGaS₂ (2.97)).     

Preparation and Crystal Structure of Au1—xSn1+yP14 and other Polyphosphides with HgPbP14‐Type Structure

The crystal structure of the known compound HgSnP₁₄ (HgPbP₁₄‐type, Pnma, Z = 4) was refined from single‐crystal X‐ray diffractometer data to a residual of R = 0.067 for 1470 structure factors and 83 variable parameters. This polyphosphide has a smaller cell volume than the isotypic compound CdSnP₁₄. For that reason it had been suggested earlier that the mercury atoms in HgSnP₁₄ will show a tendency for linear P—Hg—P coordination. This is not supported by the present structure refinement, which shows a distorted tetrahedral phosphorus coordination for the mercury atoms, very similar to that of the cadmium atoms in CdSnP₁₄. A brief literature survey shows that quite generally the mercury atoms have a smaller volume requirement than the cadmium atoms in intermetallics and more or less covalent compositions, in contrast to more ionic compounds, where the inverse relationship is observed. Chemical bonding in HgSnP₁₄ can be rationalized on the basis of the Zintl‐Klemm concept, resulting in the formula Hg⁺²Sn⁺²(P₁₄)^—4. Accordingly, the environment of the tin atoms shows the lone pair effect. Reactions of the elemental components aiming for the isotypic compounds CuSnP₁₄, CuPbP₁₄, AgSnP₁₄, AgPbP₁₄, AuSnP₁₄, and AuPbP₁₄ resulted in microcrystalline samples. The fibrous habit and the energy dispersive X‐ray fluorescence analyses of the products indicate the formation of these polyphosphides. Only for the gold‐tin compound was it possible to isolate a single crystal suitable for a structure refinement, which confirmed its HgPbP₁₄‐type structure: a = 1259.5(3) pm, b = 982.0(2) pm, c = 1056.2(3) pm, R = 0.046 for 1520 F values and 87 variables. The gold position was found with a lower occupancy, thus resulting in the two possible extreme formulas Au_0.852(4)SnP₁₄ and Au_0.64(1)Sn_1.36(1)P₁₄, depending of whether vacancies or a mixed Au/Sn occupancy is assumed for this position. An analysis of interatomic distances suggests the latter formula to be correct with tetravalent tin on the gold sites corresponding to the formula [(Au⁺¹)_0.64(1)(Sn⁺⁴)_0.36(1)]^+2.08(3)[SnP₁₄]^—2.     

Verbindungsbildung in den quasi-binären Systemen AcX4?MX2 (Ac = Th,U; M = Ca,Sr, Ba,Eu, Ge,Sn, Pb; X = Br,I)

Formation of Compounds in the Quasi-binary Systems AcX₄? MX₂ (Ac = Th, U; M = Ca, Sr, Ba, Eu, Ge, Sn, Pb; X = Br, I) T,x-phase diagrams of the systems ThI₄? SnI₂, ThI₄? PbI₂, ThI₄? CaI₂, and ThI₄? SrI₂ were established using thermoanalysis and x-ray methods. The only ternary compounds have a 1:1 composition. Further AcMX₆ compounds (Ac: Th, U; M: Ca, Sr, Ba, Eu, Ge, Sn, Pb; X: Br, I) were synthesized and their structures investigated. Four structure types are found depending on the temperature and the Ac/M combinations. The structures of γ-ThSnI₆ and β-ThSnI₆ were determined with single crystal methods as representatives of a whole series of isotypic compounds.     

Tetra­butyl­bis(N‐phthaloyl­glycinato)­distannoxane dimer

The crystal structure of the title compound, [Sn₄(C₄H₉)₈(C₁₀H₆NO₄)₄O₂], contains centrosymmetric dimers. It contains a central Sn₂O₂ core with the O atoms bonded to two di­butyl­bis(N‐phthaloyl­glycinato)­tin units. The Sn atoms of the core are six‐coordinate in a skew trapezoidal bipyramidal geometry, while the exocyclic Sn atoms are essentially five‐coordinate in a distorted trigonal geometry. The Sn—C distances lie in a narrow range of 2.120 (5)–2.138 (4) Å.     

Verbindungen A3M5 (A = Erdalkalimetall,M = Triel/Tetrel): Eine Fallstudie zur strukturellen und elektronischen Stabilität polarer intermetallischer Phasen

Compounds A₃M₅ (A = alkaline earth, M = triel/tetrel): A Case Study on Structural and Electronic Factors Stabilizing Polar Intermetallics Starting from the non electron precise binary compounds Ca₃Ga₅/Sr₃In₅ (Hf₃Ni₂Si₃ type) and Ba₃Al₅ at one hand and Ba₃Pb₅ (Pu₃Pd₅ type) at the other hand, a series of new ternary intermetallics of the general formula A₃M₅ (A: alkaline earth, M: triel/tetrel) has been synthesized, structurally characterized and studied by band structure calculations. The chemical substitution of M in A₃M₅ allows, via the continous variation of the radius ratio (r_A:r_M) and the valence electron number (VE/M) the detection of the geometrically and electronically determined stability ranges of the three structure types formed by the binary compounds. At values of r_A:r_M between 1.30 and 1.52 in the triel rich region of A₃M′_xM″_5?x the Hf₃Ni₂Si₃ type (orthorhombic, space group Cmcm) is formed: In Ca₃Ga₅ up to 1.8 Ga can be substituted by Al, in Sr₃In₅ similar amount of In can be replaced by either Al or Ga. The mixed trielide Sr₃Al_2.6Ga_2.4 (a = 468.4(1), b = 1132.5(1), c = 1570.0(2) pm, R1 = 0.0261) can be obtained, although both corresponding binary phases are not known. At larger values of the ratio r_A/r_M as in Ba₃Al₃Ga₂ (Ba₃Al₅ type, hexagonal, space group P6₃/mmc, a = 598.9(1), c = 1456.0(3) pm, R1 = 0.0353) layers of condensed M₅ building blocks with Al‐Al partial bonds are formed. Substituting one In position in Sr₃In₅ against Pb results in the isotypic, but electron precise Zintl compound Sr₃In₄Pb (a = 506.1(1), b = 1191.8(3), c = 1650.2(4) pm, R1 = 0.0286), where the Fermi level in shifted into a distinct minimum of the density of states. Conversely, at the tetrele rich end of the series A₃In_xPb_5?x, characterized by compounds of the Pu₃Pd₅ type (orthorhombic, space group Cmcm) with almost isolated nido clusters M₅, a minimum of the DOS can be reached, if Pb is partially substituted by In (A₃In_xPb_5?x with A = Sr/Ba: x = 0.7/0.6; a = 1084.6(2)/1118.6(2), b = 867.1(2)/904.4(1), c = 1104.8(2)/1133.9(2) pm, R1 = 0.0394/0.0434).