Synthese und Kristallstrukturen von DyPt8P2 und Mg10−xPt9P7

Synthesis and Crystal Structures of DyPt₈P₂ and Mg_10?xPt₉P₇ Single crystals of DyPt₈P₂ (a = 9.260(2), b = 4.005(1), c = 9.633(2) Å, β = 102.64(3)°) were grown by heating the elements in a melt of NaCl/KCl at 1100 °C. The phosphide crystallizes in a new type of structure (I2/m; Z = 2) which consists of fragments in the shape of a cubic close packing built up by three fourths of the platinum atoms. The Dy atoms are coordinated by twelve Pt and four P atoms forming a distorted hexagonal prism which is fourfold capped by Pt atoms. Needles of Mg_10?xPt₉P₇ (a = 18.121(4), b = 23.316(5), c = 3.848(1) Å) were obtained by reaction of the elements in molten lead at 1000 °C. The main feature of the new type of structure (Pbam; Z = 4) is an oval ring of pentagonal prisms formed by each six Pt and four P atoms. The prisms are linked with each other via common faces and they are centered by Mg atoms. Another Mg atoms are located in holes of the three‐dimensional [Pt₉P₇] network. It is remarkable, that one of the ten different crystallographic sites of the Mg atoms is occupied incompletely inducing the composition Mg_10?xPt₉P₇ with x = 0.86.     

Cluster self-organization of intermetallic systems: Nanocluster precursors (i-K8, i-K6, K4) and self-assembly of crystal structures Ir8Mg58(cF396), Ir7Mg44(cF408), and Ir6Mg26 (hR96)

Suprapolyhedral cluster precursors Kn with a hierarchical structure (with the number of polyhedra n = 4, 6, 8) have been derived and their topological representation as bichromatic graphs has been performed. With the use of computer methods (the TOPOS program package), combinatorial-topological analysis of icosahedral monster structures of close compositions Ir₈Mg₅₈ (cF396, F $ \bar 4 $ 3m, V = 8139 ų) and Ir₇Mg₄₄ (cF408, F $ \bar 4 $ 3m, V = 8117 ų) has been performed. Suprapolyhedral nanoclusters consisting of eight and six Ir icosahedra (nanoclusters i-K8 and i-K6 comprising 86 and 50 atoms) have been identified by the method of complete decomposition of the 3D factor graph of crystal structures into cluster substructures in Ir₇Mg₄₄. In Ir₈Mg₅₈, the i-K8 nanocluster is retained, whereas the i-K6 cluster is substituted by the K4 nanocluster composed of four Ir polyhedra with CN = 9 comprising 34 atoms. Complete 3D reconstruction of the self-assembly mechanism of crystal structure has been carried out by the scheme nanocluster precursor-primary chain-microlayer-microframework. It has been demonstrated that the voids in the Ir₈Mg₅₈ and Ir₇Mg₄₄ frameworks accommodate tetrahedral cluster spacers T-Mg(Mg₄) and T-Mg₄, respectively. The Ir₆Mg₂₆ structure (hR96, R $ \bar 3 $ c, V = 1890 ų) is made of the suprapolyhedral cluster K6 formed by six Ir polyhedra with CN = 11 and comprising 50 atoms; in this case, the structure contains no cluster spacers. In all structures, nanoclusters retain their own symmetry ( $ \bar 4 $ 3m for i-K8, i-K6, and K4 and $ \bar 3 $ for K6).     

Mg3Ir3Si8, ein neues Magnesium‐Iridium‐Silicid mit Tetraedern und gekappten Tetraedern aus Silicium‐Atomen

Mg₃Ir₃Si₈, a New Magnesium Iridium Silicide with Si₄ Tetrahedra and Si₁₂ Truncated Tetrahedra The ternary silicide Mg₃Ir₃Si₈ (cubic, a = 1221.4(1) pm, space group , 8 formula units per unit cell) was prepared by reaction of the elemental components in a sealed molybdenum container (1000 °C, 1 d, cooled with 100 °/h). The crystal structure was determined from single crystal data. Short distances in the three‐dimensional iridium silicon network indicate strong Ir‐Si‐bonding (d(Ir‐Si) = 240.5(2) and 245.6(1) pm). In addition, homonuclear bonding seems to be important, resulting in the formation of Si₄‐tetrahedra (d(Si‐Si) = 257(1) pm), and Mg centered Si₁₂‐polyhedra with the shape of truncated tetrahedra (d(Si‐Si) = 241(1) and 261.0(9) pm). Furthermore, Mg₄‐tetrahedra with Mg‐Mg‐distances of 355(2) pm are formed. The structure may be derived from the structure of the isotypic compounds Mg₅Pd₁₀Si₁₆ and Mg₅Pt₁₀Si₁₆ by adding a Mg siteset and subtracting a platinum metal siteset. It can be described by an expanded cubic “close” packing of MgIr₆‐octahedra in which Si₄‐tetrahedra reside in the octahedral holes while Mg₄‐tetrahedra and MgSi₁₂‐units occupy one half of the tetrahedral holes each.     

Kristall‐ und elektronische Strukturen von AIr2P2 (A: Ca — Ba)

Crystal and Electronic Structures of AIr₂P₂ (A: Ca — Ba) Single crystals of CaIr₂P₂ (a = 6.610(3), c = 7.031(3)Å) were prepared by reaction of the elements in a lead flux and investigated by X‐ray methods. The compound crystallizes with the EuIr₂P₂ type (P3₂21; Z = 3) just detected in the case of SrIr₂P₂. In the structure all the P atoms and half of the Ir atoms build a three‐dimensional framework with Ca and the remaining Ir atoms in the cavities. The latter atoms form threefold screws along [001] with relatively short Ir‐Ir distances and they are connected with the framework by Ir‐P bonds. LMTO band structure calculations suggested that the compounds with Ca, Sr, and Eu should be semiconductors. For EuIr₂P₂ this was confirmed by conductivity measurements. BaIr₂P₂ (a = 3.946(1), c = 12.572(2)Å) synthesized by heating the elements at 1050 °C for a long time crystallizes with the ThCr₂Si₂ type structure (I4/mmm; Z = 2). Due to the rigid layers of IrP₄ tetrahedra and the atomic size of barium the P‐P distance between the layers with a value of 3.71Å is very long.     

Das neue ternäre Borid Mg8Pt4B und die neue intermetallische Verbindung PtMg2

The New Ternary Boride Mg₈Pt₄B and the New Intermetallic Compound PtMg₂ The new magnesium platinum boride Mg₈Pt₄B was obtained from a reaction of the elements in sealed niobium tubes. It crystallizes isotypically with Mg₈Rh₄B in the cubic space group with a =12.2481(1) Å and can be structurally derived from the Ti₂Ni structure type, where boron occupies cavities, which are formed by four magnesium and four platium atoms. The new intermetallic compound PtMg₂ was also prepared by reaction of the elements in a sealed Nb container and adopts the tetragonal CuAl₂ type structure, space group I4/mcm with a = 6.334(1) Å and c = 5.621(1) Å.     

Synthese und Kristallstrukturen der Calcium‐Iridiumsilicide Ca3Ir4Si4 und Ca2Ir2Si

Synthesis and Crystal Structures of the Calcium Iridium Silicides Ca₃Ir₄Si₄ and Ca₂Ir₂Si The new compounds Ca₃Ir₄Si₄ und Ca₂Ir₂Si were prepared by reaction of the elemental components in sealed tantalum ampoules at 1200 °C. Their structures were determined from X‐ray single crystal data. Ca₃Ir₄Si₄(cubic, space group I4¯3m, a = 7.4171(2)Å, Z = 2) crystallizes with the Na₃Pt₄Ge₄ type structure. For Ca₂Ir₂Si (monoclinic, space group C2/c, a = 9.6567(5)Å, b = 5.8252(2)Å, c = 7.3019(4)Å, β = 100.212(2)°, Z = 4) a new structure was found. Chains of edge sharing, heavily distorted SiIr₄‐tetrahedra (Ir‐Si: 2.381 and 2.414Å) are connected via short Ir—Ir‐contacts (2.640Å) to form an open Ir/Si‐framework accommodating a three‐dimensional arrangement of calcium atoms (Ca—Ca: 3.413 ‐ 3.948Å).     

The IrX6 Coordination Polyhedra (X = F,Cl, Br) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of compounds containing [Ir _a X _b ] ^z– complexes (X = F, Cl, or Br). The coordination number of Ir atoms with respect to halogen atoms was found to be 6, irrespective of the oxidation state (III, IV, or V), and the coordination polyhedra formed by Ir were found to be always octahedra. The influence of the site symmetry and the valence state of the Ir atoms on the distortion of the IrX₆ octahedra is considered. It is shown that characteristics of the VDP of Ir atoms can be used for quantitative estimation of the crystal-chemical role of Ir atoms in the halide structures.     

Spatial Separation of Covalent,Ionic, and Metallic Interactions in Mg11Rh18B8 and Mg3Rh5B3

The crystal structures of Mg₁₁Rh₁₈B₈ and Mg₃Rh₅B₃ have been investigated by using single‐crystal X‐ray diffraction. Mg₁₁Rh₁₈B₈: space group P4/mbm; a=17.9949(7), c=2.9271(1) Å; Z=2. Mg₃Rh₅B₃: space group Pmma; a=8.450(2), b=2.8644(6), c=11.602(2) Å; Z=2. Both crystal structures are characterized by trigonal prismatic coordination of the boron atoms by rhodium atoms. The [BRh₆] trigonal prisms form arrangements with different connectivity patterns. Analysis of the chemical bonding by means of the electron‐localizability/electron‐density approach reveals covalent B? Rh interactions in these arrangements and the formation of B? Rh polyanions. The magnesium atoms that are located inside the polyanions interact ionically with their environment, whereas, in the structure parts, which are mainly formed by Mg and Rh atoms, multicenter (metallic) interactions are observed. Diamagnetic behavior and metallic electron transport of the Mg₁₁Rh₁₈B₈ and Mg₃Rh₅B₃ phases are in agreement with the bonding picture and the band structure.     

Neue ternäre Rhodium‐ und Iridium‐Phosphide und ‐Arsenide mit U4Re7Si6‐Struktur

New Ternary Rhodium‐ and Iridium‐Phosphides and ‐Arsenides with U₄Re₇Si₆ Type Structure Single crystals of Mg₄Rh₇P₆ (a = 7.841(1) Å), Mg₄Rh₇As₆ (a = 8.066(1) Å), Yb₄Rh₇As₆ (a = 8.254(1) Å) and Mg₄Ir₇As₆ (a = 8.082(2) Å) were prepared by heating mixtures of the elements in a lead flux and were investigated by means of X‐ray methods. The compounds are isotypic and they crystallize in the U₄Re₇Si₆ type structure (Im 3 m; Z = 2), which is formed by CeMg₂Si₂ analogous units, which are twisted against each other. The Rh(Ir) atoms building these units are coordinated tetrahedrally by the non‐metal. The P(As) atoms of six units form a regular octahedron, which is centred by an additional Rh(Ir) atom. This second structural segment corresponds to the perovskit type structure.     

Synthese und Kristallstrukturen des Zink‐Rhodiumborids Zn5Rh8B4 und der Lithium‐ Magnesium‐Rhodiumboride LixMg5−xRh8B4 (x = 1.1 und 0.5) und Li8Mg4Rh19B12

Synthesis and Crystal Structures of Zinc Rhodium Boride Zn₅Rh₈B₄ and the Lithium Magnesium Rhodium Borides Li_xMg_5?xRh₈B₄ (x = 1.1 and 0.5) and Li₈Mg₄Rh₁₉B₁₂ The title compounds were prepared by reaction of the elemental components in metal ampoules under argon atmosphere (1100 °C, 7 d). In the case of Zn₅Rh₈B₄ (orthorhombic, space group Cmmm, a = 8.467(2) Å, b = 16.787(3) Å, c = 2.846(1) Å, Z = 2) a BN crucible enclosed in a sealed tantalum container was used. The syntheses of Li_xMg_5?xRh₈B₄ (orthorhombic, space group Cmmm, Z = 2, isotypic with Zn₅Rh₈B₄, lattice constants for x = 1.1: a = 8.511(3) Å, b = 16.588(6) Å, c = 2.885(1) Å, and for x = 0.5: a = 8.613(1) Å, b = 16.949(3) Å, c = 2.9139(2) Å) and Li₈Mg₄Rh₁₉B₁₂ (orthorhombic, space group Pbam, a = 26.210(5) Å, b = 13.612(4) Å, c = 2.8530(5) Å, Z = 2) were carried out in tantalum crucibles enclosed in steel containers using lithium as a metal flux. The crystal structures were solved from single crystal X‐ray diffraction data. In both structures Rh atoms reside at z = 0 and all non‐transition metal atoms at z = 1/2. Columns of Rh₆B trigonal prisms running along the c‐axis are laterally connected to form three‐dimensional networks with channels of various cross sections containing Li‐, Mg‐, and Zn‐atoms, respectively. A very short Li‐Li distance of 2.29(7) Å is observed in Li₈Mg₄Rh₁₉B₁₂.     

Neue Germanide mit geordneter Ce3Pt4Ge6‐Struktur – Die Verbindungen Ln3Pt4Ge6 (Ln: Pr–Dy)

New Germanides with an Ordered Variant of the Ce₃Pt₄Ge₆ Type of Structure – The Compounds Ln₃Pt₄Ge₆ (Ln: Pr–Dy) Six new germanides Ln₃Pt₄Ge₆ with Ln = Pr–Dy were synthesized by heating mixtures of the elements at 900 °C, annealing the inhomogeneous powders at 1050‐1100 °C for six days and then cooling down from 700 °C in the course of two months. The crystal structures of Pr₃Pt₄Ge₆ (a = 26.131(5), b = 4.399(1), c = 8.820(2) Å), Sm₃Pt₄Ge₆ (a = 25.974(3), b = 4.356(1), c = 8.748(1) Å), and Dy₃Pt₄Ge₆ (a = 26.079(5), b = 4.311(1), c = 8.729(2) Å) were determined by single crystal X‐ray methods. The compounds are isotypic (Pnma, Z = 4) and crystallize with an ordered variant of the Ce₃Pt₄Ge₆ type of structure (Cmcm, Z = 2) consisting of CaBe₂Ge₂‐ and YIrGe₂‐analogous units. The platinum atoms are located in distorted square pyramids of germanium atoms and build up with them a three‐dimensional network. The coordination polyhedra of the platinum and germanium atoms around the rare‐earth metal atoms are pentagonal and hexagonal prisms. These are completed by some additional atoms resulting in coordination numbers of 14 and 15 respectively. The other germanides were investigated by powder methods resulting in the following lattice constants: a = 26.067(6), b = 4.388(1), c = 8.800(2) Å for Ln = Nd; a = 25.955(7), b = 4.337(1), c = 8.728(2) Å for Ln = Gd; a = 25.944(5), b = 4.322(1), c = 8.698(2) Å for Ln = Tb. The atomic arrangement of Ln₃Pt₄Ge₆ is compared with the well‐known monoclinic structure of Y₃Pt₄Ge₆.     

Mg15Ir5Si2, ein Magnesium‐Iridiumsilicid mit isolierten Ir5Si2‐Baugruppen

Mg₁₅Ir₅Si₂ a Magnesium Iridium Silicide with Isolated Ir₅Si₂ Building Groups Mg₁₅Ir₅Si₂ (tetragonal, P4₂/n, a = 1371.7(1) pm, c = 873.0(2) pm, Z=4, 1497 reflections, 103 parameters, R1 = 0.048) was prepared by reaction of the elements at 900 °C in sealed tantalum ampoules. The compound is the silicide with the highest alkaline earth metal content known so far. It is the first example of a silicide with an isolated transition metal silicon building group embedded in a matrix of non‐transition metal atoms. The structure contains planar Ir₂SiIrSiIr₂ groups with silicon atoms in nearly trigonal planar coordination of three iridium atoms (d_Ir‐Si = 235 and 236 pm).     

Darstellung und Kristallstruktur von ANi10P3 (A: Zn,Ga, Sn,Sb)

Preparation and Crystal Structure of A Ni₁₀P₃ ( A : Zn, Ga, Sn, Sb) Four compounds ANi₁₀P₃ (A: Zn, Ga, Sn, Sb) were prepared by heating mixtures of the elements and investigated by means of X‐ray methods. Single crystal structure determinations of ZnNi₁₀P₃ (a = 7.665(1), c = 9.360(1) Å) and SnNi₁₀P₃ (a = 7.674(1), c = 9.621(1) Å) respectively showed, that they are isotypic and crystallize in a new structure (P3m1; Z = 3). This type is characterized by 3²⁰ and 3²⁴ cages of Ni atoms (Frank Kasper polyhedra), which are connected with each other. A atoms are located in the centres of these polyhedra and have no direct bonds to the P atoms.     

Rare‐Earth‐Rich Magnesium Compounds RE23Rh7Mg4 (RE = La,Ce, Pr,Nd, Sm,Gd) with Tetrahedral Mg4 Clusters

The rare earth‐rich compounds RE₂₃Rh₇Mg₄ (RE = La, Ce, Pr, Nd, Sm, Gd) were prepared by induction‐melting the elements in sealed tantalum tubes. The new compounds were characterized by X‐ray powder diffraction. They crystallize with the hexagonal Pr₂₃Ir₇Mg₄ type structure, space group P6₃mc. The structures of La₂₃Rh₇Mg₄ (a = 1019.1(1), c = 2303.7(4) pm, wR2 = 0.0827, 1979 F² values, 69 variables), Nd₂₃Rh₇Mg₄ (a = 995.4(2), c = 2242.3(5) pm, wR2 = 0.0592, 2555 F² values, 74 variables) and Gd₂₃Rh_6.86(5)Mg₄ (a = 980.5(2), c = 2205.9(5) pm, wR2 = 0.0390, 2083 F² values, 71 variables) were refined from single crystal X‐ray diffractometer data. The three crystallographically different rhodium atoms have trigonal prismatic rare earth coordination with short RE–Rh distances (283–300 pm in Nd₂₃Rh₇Mg₄). The prisms are condensed via common edges, leading to a rigid three‐dimensional network in which isolated Mg₄ tetrahedra (312–317 pm Mg–Mg in Nd₂₃Rh₇Mg₄) are embedded. Temperature dependent magnetic susceptibility data of Ce₂₃Rh₇Mg₄ indicate Curie‐Weiss behavior with an experimental magnetic moment of 2.52(1) μ_B/Ce atom, indicative for stable trivalent cerium. Antiferromagnetic ordering is evident at 2.9 K.     

Mg2[BN2]Cl and Mg8[BN2]5I: Novel Magnesium Nitridoborate Halides — Syntheses,Crystal Structures,and Vibrational Spectra

The title compounds have been synthesized at 1473 K from stoichiometric mixtures of the binary components Mg₃N₂, MgX₂ (X = Cl, I) and BN in arc‐welded steel ampoules encapsulated in evacuated silica tubes. Mg₂[BN₂]Cl ( 1 ) and Mg₈[BN₂]₅I ( 2 ) crystallize in the orthorhombic space groups Pbca (no. 61) and Imma (no. 74), respectively, with a = 6.6139(8)Å, b = 9.766(1)Å, c = 10.600(1)Å, Z = 8 for 1 and a = 13.535(3)Å, b = 9.350(2)Å, c = 11.194(2)Å, Z = 4 for 2 . The crystal structures are characterized mainly by Mg₆ trigonal prisms which are condensed to 3D frameworks in different ways. Part of the trigonal prisms are centered by the [N—B—N]^3— anions and other voids in the framework by the X^— anions. The magnesium environment around Cl^— is a very distorted monocapped trigonal prism (CN = 6+1) and that of I^— is a bicapped heptagonal prism (CN = 14+2). The bond lengths and bond angles for the relevant [BN₂]^3— anions are d(B—N) = 1.330 — 1.338Å, ∠N—B—N = 175.8° in 1 and d(B—N) = 1.330 — 1.339Å, ∠N—B—N = 176.8° — 178.0° in 2 . The vibrational spectra of the title compounds have been recorded and interpreted based on the D_∞h symmetry of the relevant [N—B—N]^3— groups considering the site symmetry splitting.     

Synthese und Kristallstrukturen ternärer Phosphide und Arsenide des Rhodiums und Iridiums

Ternary Phosphides and Arsenides of Rhodium and Iridium: Synthesis and Crystal Structures Single crystals of eight new compounds were prepared by heating mixtures of the elements in a lead flux. They were investigated by X‐ray methods. Ca₂Ir₁₂P₇ (a = 9.512(1), c = 3.923(1) Å)is an additional representative of the Zr₂Rh₁₂P₇ type structure, micro domains required refinements of the structural parameters in space group P6₃/m. Ca₅Rh₁₉P₁₂ (a = 12.592(1), c = 3.882(1) Å) and Ca₅Ir₁₉P₁₂ (a = 12.577(2), c = 3.954(1) Å) crystallize with the Ho₅Ni₁₉P₁₂ type structure (P6¯2m; Z = 1), whereas the compounds A₆Rh₃₀X₁₉ form a slightly modified structure of the Yb₆Co₃₀P₁₉ type. The lattice constants are: Ca₆Rh₃₀P₁₉: a = 15.532(1) Å, c = 3.784(1) Å Sr₆Rh₃₀As₁₉: a = 16.135(2) Å, c = 3.916(1) Å Eu₆Rh₃₀P₁₉: a = 15.566(1) Å, c = 3.821(1) Å Eu₆Rh₃₀As₁₉: a = 16.124(1) Å, c =5 3.903(3) Å Yb₆Rh₃₀P₁₉: a = 5 15.508(1) Å, c =5 3.770(1) Å Because one of the four non‐metal atoms, located on different crystallographic sites, is disordered along [001] micro domains are formed. Therefore the parameters were not refined in space group P6¯ (Yb₆Rh₃₀P₁₉ type), but in space group P6₃/m. The metal:non‐metal ratio of all compounds is in the range of 2:1. Accordingly most of the non‐metal atoms are coordinated by nine metal atoms, which form tricapped trigonal prisms. These polyhedra are combined with each other in a different way.     

syn‐Tri‐μ‐chlorido‐bis{[(R,R)/(S,S)‐2,2′‐bis(diphenylphosphino)‐1,1′‐biphenyl]hydridoiridium(III)} tetrafluoridoborate dichloromethane disolvate

In the structure of the title compound, [Ir₂Cl₃H₂(C₃₆H₂₈P₂)₂]BF₄·2CH₂Cl₂, the bimetallic cation features a confacial bioctahedral structure that is held together by three bridging chloride ions and is very close to C₂ symmetric. The hydrides are in a syn orientation (trans to the same halide bridge), and the chelating bis(phosphine) atropisomers display a racemic (R,R)/(S,S) configuration. Because of the high trans‐bond‐weakening influence of the hydride ligands, the Ir—Cl bonds trans to Ir—H [2.5262 (7) and 2.5365 (7) Å] are significantly longer than those opposite the Ir—P linkages [2.4287 (7)–2.4672 (8) Å]. The Ir—P distances vary between 2.2464 (9) and 2.2565 (8) Å. This study illustrates the usefulness of sterically demanding biaryl‐based P₂ ligands in the synthesis of halide‐bridged Ir₂ complexes, which are valuable precursors of versatile catalysts for homogeneous C=O hydrogenation.     

Structure and Bonding of the Mixed‐Valent Platinum Trihalides,PtCl3 and PtBr3

The isotypical crystal structures of the mixed valent trihalides PtCl₃ and PtBr₃ were redetermined by single crystal methods (space group R3¯; trigonal setting; PtCl₃: a = 21.213Å, c = 8.600Å, c/a = 0.4054; Z = 36; 1719 hkl; R = 0.035; PtBr₃: a = 22.318Å, c = 9.034Å; c/a = 0.4048; Z = 36; 1606 hkl; R = 0.027). A cubic closest packing of X^— anions forms the basis of an optimized arrangement of cuboctahedrally [Pt₆X₁₂] cluster molecules with Pt^II and enantiomers of helical chains of edge‐condensed [PtX₂X_4/2] octahedra with Pt^IV in cis‐Δ‐ and cis‐Λ‐configuration, respectively. The bond lengths vary with the function of the X^— ligands (d¯(Pt^II—X) = 2.315 and 2.445Å; d¯(Pt^II—Pt^II) = 3.336 and 3.492Å; d(Pt^IV—X) = 2.286 — 2.417Å and 2.437 — 2.563Å). The Pt^II atoms are shifted outwards the X₁₂ cuboctahedra by 0.045Å and 0.024Å, respectively. The symmetry governed Periodic Nodal Surface, PNS, perfectly separates the regions of different valencies. Quantum chemical calculations exclude the possible additional interactions between Pt^II and one of the exo‐ligands of Pt^IV.     

Structure and 31P NMR spectroscopy of a new phosphate,Na8Ca1.5Mg12.5(PO4)12

A new phosphate, sodium calcium magnesium tetrakis(phosphate), Na₈Ca_1.5Mg_12.5(PO₄)₁₂, has been synthesized by a flux method. Its novel structure consists of MgO_x (x = 5 and 6) polyhedra and MO₇ (M = Mg or Na) octahedra linked directly through common corners or edges to form a rigid three‐dimensional skeleton, reinforced by corner‐sharing between identical Mg₁₂MO₄₈ units. The connection of these units by the PO₄ tetrahedra induces cavities and crossing tunnels where the Na⁺ and Ca²⁺ cations are located. This structural model was supported by a ³¹P NMR spectroscopy study which confirmed the existence of 12 crystallographically independent sites for the P atoms.     

Two‐ and Three‐Dimensional [IrSi] Networks in the Silicides Sm3Ir2Si2, HoIrSi,and YbIrSi

New intermetallic rare earth iridium silicides Sm₃Ir₂Si₂, HoIrSi, and YbIrSi were synthesized by reaction of the elements in sealed tantalum tubes in a high‐frequency furnace. The compounds were investigated by X‐ray diffraction both on powders and single crystals. HoIrSi and YbIrSi crystallize in a TiNiSi type structure, space group Pnma: a = 677.1(1), b = 417.37(6), c = 745.1(1) pm, wR2 = 0.0930, 340 F² values for HoIrSi, and a = 667.2(2), b = 414.16(8), c = 742.8(2) pm, wR2 = 0.0370, 262 F² values for YbIrSi with 20 parameters for each refinement. The iridium and silicon atoms build a three‐dimensional [IrSi] network in which the holmium(ytterbium) atoms are located in distorted hexagonal channels. Short Ir–Si distances (246–256 pm in YbIrSi) are indicative for strong Ir–Si bonding. Sm₃Ir₂Si₂ crystallizes in a site occupancy variant of the W₃CoB₃ type: Cmcm, a = 409.69(2), b = 1059.32(7), c = 1327.53(8) pm, wR2 = 0.0995, 383 F² values and 27 variables. The Ir1, Ir2, and Si atoms occupy the Co, B2, and B1 positions of W₃CoB₃, leading to eight‐membered Ir₄Si₄ rings within the puckered two‐dimensional [IrSi] network. The Ir–Si distances range from 245 to 251 pm. The [IrSi] networks are separated by the samarium atoms. Chemical bonding in HoIrSi, YbIrSi, and Sm₃Ir₂Si₂ is briefly discussed.