Synthesis,crystal structure and chemical bonding of the novel compound IrGa2

The crystal structure of the novel constant composition compound IrGa₂ was determined from X-ray single-crystal diffraction data. The compound crystallizes in the space group Cmcm with the lattice parameters a=3.9021(3) Å, b=12.9925(8) Å and c=10.8808(7) Å. Its structure represents a new type with the Pearson symbol oC36. Analysis of the electron localization function (ELF) showed that the d electrons of both iridium atoms in IrGa₂ are involved in the bonding and that the two crystallographically independent iridium atoms have different bonding character.     

New ternary germanides La4Mg5Ge6 and La4Mg7Ge6: crystal structure and chemical bonding

The synthesis, structural characterization, and chemical-bonding peculiarities of the two new polar lanthanum-magnesium germanides La(4)Mg(5)Ge(6) and La(4)Mg(7)Ge(6) are reported. The crystal structures of these intermetallics were determined by single-crystal X-ray diffraction analysis. The La(4)Mg(5)Ge(6) phase crystallizes in the orthorhombic Gd(4)Zn(5)Ge(6) structure type [Cmc2(1), oS60, Z = 4, a = 4.5030(7) ?, b = 20.085(3) ?, c = 16.207(3) ?, wR2 = 0.0451, 1470 F(2) values, 93 variables]. The La(4)Mg(7)Ge(6) phase represents a new structure type with a monoclinic unit cell [C2/m, mS34, Z = 2, a = 16.878(3) ?, b = 4.4702(9) ?, c = 12.660(3) ?, β = 122.25(3)°, wR2 = 0.0375, 1466 F(2) values, 54 variables]. Crystallographic analysis together with linear muffin-tin orbital band structure calculations reveals the presence of strongly bonded 3D polyanionic [Mg-Ge] networks balanced by positively charged La atoms in both stoichiometric compounds. The La(4)Mg(5)Ge(6) compound is related to Zintl phases, showing a prominent density of states pseudogap at the Fermi level. A distinctive feature of the La(4)Mg(5)Ge(6) structure is the presence of Ge-Ge covalent dumbbells; in La(4)Mg(7)Ge(6), the higher Mg content generates a polyanionic network consisting exclusively of Mg-Ge heterocontacts. Nevertheless, the frameworks of the two phases are structurally similar, as is highlighted in this work.     

1-Phosphinodiazaphosphene: Synthesis,crystal structure,and bonding properties

The iminophosphane, tBu₂P PN NR₂ (RSiMe₃), produced by base-catalyzed elimination of ClSiMe₃ from the corresponding phosphane, possesses an unusually long PN bond (162 pm), which is in accord with quantum chemical calculations.     

The binary gallide Eu5Ga9 - crystal structure, chemical bonding and physical properties

The title compound was prepared from the elements by reaction in a sealed tantalum tube at 1320 K followed by slow cooling to 970 K or, alternatively, in glassy carbon crucibles with HF melting. The crystal structure of Eu₅Ga₉ was refined from single-crystal data: Cmcm, a=4.613(1) Å, b=10.902(3) Å, c=26.097(6) Å, Z=4, R_F=0.036, 811 structure factors and 46 variables. The structure is described as a three-dimensional network formed by gallium atoms with europium atoms embedded in the cavities. The bonding analysis (LMTO, ELF) confirmed this representation of the structure. Magnetic susceptibility measurements show Curie-Weiss behavior above 60 K with a magnetic moment per Eu atom of 8.12(1) μ_B, indicating divalent europium. Eu₅Ga₉ orders antiferromagnetically at 19.0(5) K with re-ordering at 6.0(5) K. The electrical resistivity shows a metallic temperature dependence and magnetic scattering. ¹⁵¹Eu Mössbauer spectroscopic experiments are compatible with divalent europium and show complex magnetic hyperfine field splitting below the ordering temperature.     

Crystal structure and chemical bonding of Mg3Ru2

Mg 3Ru 2 was prepared by a reaction between the elements in the ideal ratio in a sealed tantalum ampule. Its beta-manganese type crystal structure was refined on the basis of the single-crystal data: space group P4 132, a = 693.52(6) pm, wR2 = 0.024, 168 F (2) values, and 10 parameters. The magnesium (CN = 14) and ruthenium (CN = 12) atoms are completely ordered on the 12d and 8c sites of the crystal structure of beta-manganese. Both environments can be considered as Frank-Kasper related polyhedra. A periodic nodal surface P4 132(110) pi (1) P4 132 separates the magnesium and ruthenium positions in two different labyrinths, suggesting different chemical interactions within different parts of the structural motif. Analysis of the chemical bonding with the electron localizability indicator (ELI-D) reveals covalently interacting three-bonded ruthenium atoms, forming a 3D network. The network interacts with the magnesium substructure by multicenter bonds.     

Synthesis,crystal structure and properties of three ternary dysprosium 2-halogenated benzoic acid complexes

Three ternary dysprosium complexes [Dy(2-ClBA)₃?·?phen]₂ (1), [Dy(2-ClBA)₃?·?2,2′-bipy]₂ (2), and [Dy(2-BrBA)₃?·?phen]₂ (3) (where 2-ClBAH?=?2-ClC₆H₄COOH, 2-BrBAH?= 2-BrC₆H₄COOH, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipyridine) have been synthesized and characterized by X-ray single crystal diffraction. Complex 1 consists of two independent binuclear molecules, [Dy(2-ClBA)₃?·?phen]₂ (a) and [Dy(2-ClBA)₃?·?phen]₂ (b), in which the coordination environment is similar. Each Dy³⁺ is nine coordinate with two nitrogens from phen and seven oxygens from five 2-ClBA groups. 2-ClBA groups coordinate to Dy³⁺ in three ways, bidentate chelating, bidentate-bridging and terdentate-bridging. Complexes 2 and 3 consist of one binuclear molecule. The crystal structure of 2 is similar to that of binuclear molecule (a) or (b) of complex 1. In 3, each Dy³⁺ ion is eight-coordinate by two nitrogens from phen and six oxygens from five 2-BrBA groups. 2-BrBA groups coordinate to the Dy³⁺ ion in two ways, bidentate chelating and bidentate-bridging. The complexes were studied by UV, DTA-TG, and fluorescence spectrometry.     

Synthesis, crystal structure and some physical properties of RuZn3

The crystal structure, phase relations and some physical properties of the binary zinc-rich phase RuZn3 are reported. The title compound is accessible via high-temperature reaction from the elements in the appropriate substance amount ratio. Its crystal structure was determined from a Rietveld profile fit to an X-ray diffractogram of pristine RuZn3 and confirmed by single-crystal X-ray structure analysis. The title compound adopts a tetragonal Al3Zr-type structure corresponding to an A2B2 anti-phase domain structure of the cubic AuCu3-type: a=376.82(3) pm, c=1554.78(13) pm, I4/mmm, Z=4, R(F)(all data)=0.0197, 153 unique reflections, 12 variables. The structure is discussed in the light of the Hume-Rothery concept. RuZn3 melts at 1373(2) K, is a moderate metallic conductor (rho(293 K)=6.2 mOmega cm) and exhibits basically temperature-independent paramagnetic properties. It coexists with Ru1-xZnx and RuZn6.     

Synthesis, crystal structure, magnetic properties, and electronic structure of the new ternary vanadate CuMnVO4

A new magnetic oxide, CuMnVO4, was prepared, and its crystal structure was determined by single-crystal X-ray diffraction. The magnetic properties of CuMnVO4 were characterized by magnetic susceptibility and specific heat measurements, and the spin exchange interactions of CuMnVO4 were analyzed on the basis of spin-polarized electronic band structure calculations. CuMnVO4 contains MnO4 chains made up of edge-sharing MnO6 octahedra containing high-spin Mn2+ cations. Our work shows that CuMnVO4 undergoes a three-dimensional antiferromagnetic transition at approximately 20 K. Both the intrachain and interchain spin exchanges are antiferromagnetic, and the interchain spin exchange is not negligible compared to the intrachain spin exchange.     

Synthesis,structure, and physical properties of the new layered ternary chalcogenide NbNiTe5

The new ternary chalcogenide NbNiTe₅ has been prepared. NbNiTe₅ crystallizes with four formula units in a cell with dimensions a = 3.656(5), b = 13.075(16), c = 15.111(19) Å in the orthorhombic system in space group D¹⁷_2h-Cmcm. The structure has been refined to a final R index on F²_o of 0.037 for 25 variables and 1405 observations. NbNiTe₅ forms in a new layered structural type. Each layer consists of bicapped trigonal prismatic niobium atoms and octahedral nickel atoms coordinated by tellurium atoms. Electrical conductivity measurements indicate that NbNiTe₅ is a metal; its conductivity at room temperature is about 1.3 × 10⁴ Ω⁻¹ cm⁻¹. Magnetic susceptibility measurements show that NbNiTe₅ is paramagnetic (X_rt ≈ 1.04 × 10⁻³ emu mole⁻¹).     

Synthesis, crystal structure, and physical properties of sterically unprotected hydrocarbon radicals

We have prepared and isolated neutral polycyclic hydrocarbon radicals. A butyl-substituted radical gave single crystals, in which a π-dimeric structure, not a σ-bonded dimer, was observed, even though steric protection was absent. Thermodynamic stabilization due to the highly spin-delocalized structure contributes effectively to the suppression of σ-bond formation.     

Synthesis, structure and physical properties of the new uranium ternary phase U3Co2Ge7

A new ternary compound, U₃Co₂Ge₇, has been synthesized from the corresponding elements by a high temperature reaction using molten tin flux. It crystallizes in the orthorhombic La₃Co₂Sn₇-type (Pearson's symbol oC24, space group Cmmm, No. 65) with lattice parameters determined from single-crystal X-ray diffraction as follows: a=4.145(2) Å; b=24.920(7); c=4.136(2) Å, V=427.2(3) Å³. Structure refinements confirm an ordered structure having two crystallographically inequivalent uranium atoms, occupying sites with dissimilar coordination. U₃Co₂Ge₇ orders ferromagnetically below 40 K and undergoes a consecutive magnetic transition at 20 K. These results have been obtained from temperature- and field-dependent magnetization, resistivity and heat-capacity measurements. The estimated Sommerfeld coefficient γ=87 mJ/mol-U K² suggests U₃Co₂Ge₇ to be a moderately heavy-fermion material.     

Synthesis and crystal structure of Na2CaP2O7

Na₂CaP₂O₇ has been prepared in single crystal form by fusion techniques. The single crystal structure: a = 5.361(3), b = 7.029(3), c = 8.743(4)Å, α = 69.40(2), β = 89.02(3), γ = 88.78(4) °, V = 308.5(3)ų, space group P1 bar, Z = 2, D_calc = 2.799 mg/m³, R/R_w = 0.0445/0.0554 for 1434 observed reflections (F>4.0σ(F), shows a solid state form similar to that of K₂SrP₂O₇, K₂MnP₂O₇ and KaCdP₂O₇.     

CuAl2 revisited: Composition, crystal structure, chemical bonding, compressibility and Raman spectroscopy

The structure of CuAl₂ is usually described as a framework of base condensed tetragonal antiprisms [CuAl_8/4]. The appropriate symmetry governed periodic nodal surface (PNS) divides the space of the structure into two labyrinths. All atoms are located in one labyrinth, whereas the second labyrinth seems to be ‘empty’. The bonding of the CuAl₂ structure was analyzed by the electron localization function (ELF), crystal orbital Hamiltonian population (COHP) analysis and Raman spectroscopy. From the ELF representation it is seen, that the ‘empty’ labyrinth is in fact the place of important covalent interactions. ELF, COHP in combination with high-pressure X-ray diffraction and Raman spectroscopy show that the CuAl₂ structure is described best as a network built of interpenetrating graphite-like nets of three-bonded aluminum atoms with the copper atoms inside the tetragonal-antiprismatic cavities.     

Synthesis,structure, physical properties,and electronic structure of KGaSe2

The ternary gallium selenide KGaSe₂ has been synthesized by solid-state reactions and good quality crystal has been obtained. KGaSe₂ crystallizes in the monoclinic space group C2/c with cell dimensions of a = 10.878(2) Å, b = 10.872(2) Å, c = 15.380(3) Å, and β = 100.18(3)°. In the structure, adamantane like [Ga₄Se₁₀]⁸⁻ units are connected by common corners forming two-dimensional [GaSe₂]⁻ layers which are separated by K⁺ cations. KGaSe₂ exhibits congruent-melting behavior at around 965 °C. It is transparent in the range of 0.47–20.0 μm and has a band gap of 2.60(2) eV. From a band structure calculation, KGaSe₂ is a direct-gap semiconductor. The band gap is mainly determined by the [GaSe₂]⁻ layer.     

Synthesis and crystal structure of MgB12Si2—The first ternary compound in the system B/Mg/Si

We report on the synthesis of MgB₁₂Si₂ the first ternary compound in the system B/Mg/Si. Yellow transparent single crystals were yielded from the elements at 1600 °C in h-BN crucibles welded in Ta ampoules. MgB₁₂Si₂ crystallizes orthorhombic in the space group Pnma with , , and Z=4. The crystal structure is characterized by layers of B₁₂ icosahedra, connected by isolated Si atoms to a three-dimensional framework. Mg atoms are placed in voids of the framework. Each icosahedron forms 8 B-Si bonds and 4 exohedral B-B bonds. The Si atoms are tetrahedrally coordinated by B atoms of the B₁₂ icosahedra.     

Synthesis and physical chemical properties of Ca-substituted LaTiO2N

Oxynitrides with the general formula La_1−xCa_xTiO_2+xN_1−x (x = 0, 0.3, 0.5, 0.7, 1.0) were synthesized by thermal ammonolysis of oxide precursors produced with a soft chemistry method. The crystallographic structure, optical properties and the thermal stability of the compounds were studied with X-ray diffraction, UV–vis spectroscopy and thermal analysis.

All materials crystallize in perovskite-type pseudo-cubic unit cell. It was found that the lattice parameter decreases with increasing Ca content, while the optical band gap width increases with increasing x. Thermal reoxidation studies of the synthesized materials reveal the formation of nitrogen rich intermediates. The decomposition rate of the intermediates was correlated with the structure of the final products. TEM studies show a preferred insertion direction of the nitrogen into the crystal lattice of the starting oxides. Ammonolysis with flux significantly changed the microstructure of the obtained oxynitrides.     

Synthesis, chemical bonding and physical properties of RERhB4 (RE=Y, Dy-Lu)

The compounds of rare-earth metals with rhodium and boron RERhB₄ (RE=Y, Dy-Lu) crystallize with the orthorhombic structure type YCrB₄ (space group Pbam, Pearson symbol oP24). The crystal structures of the compounds with RE=Y, Er, Tm and Yb were refined by using single-crystal diffraction data. Analysis of chemical bonding for YRhB₄ and YbRhB₄ was performed by electron localizability indicator and by calculation of quantum chemical charges (quantum theory of atoms in molecules). Boron and rhodium form the 3-D polyanion containing planar nets of three-bonded boron atoms interconnected by rhodium along [001]. The interaction of the RE species with the rhodium-boron polyanion is predominantly ionic. Magnetic susceptibility data of TmRhB₄ and YbRhB₄ showed that the RE species are in 4f¹² (Tm) and 4f¹³ (Yb) electronic states, respectively. In the low-temperature region, the specific heat revealed a Schottky anomaly for TmRhB₄ while an antiferromagnetic transition is observed at 3.5 K for YbRhB₄. X-ray absorption measurement at the Yb L_III edge for YbRhB₄ reveals the 4f¹³ state of ytterbium.     

Synthesis and crystal structure of a novel ternary oxoborate, PbBiBO4

A novel ternary borate oxide, lead bismuth boron tetraoxide, PbBiBO₄, has been prepared by solid-state reaction at temperature below 800 °C. The single-crystal X-ray structural analysis showed that PbBiBO₄ crystallizes in the monoclinic space group P2₁/n with , , , β=91.48(1), Z=4. It represents a new structure type in which distorted BiO₆⁹⁻ octahedra are connected to each other in corner- and edge-sharing manner to form two-dimensional layers that are bridged by B atoms of BO₃ triangles giving rise to a three-dimensional framework, with channels parallel to the [0 1 0] direction accommodating the pyramidally coordinated Pb²⁺ cations.     

Synthesis, structure, and physical properties of Ce2PdGa10

A new ternary compound, Ce₂PdGa₁₀, has been synthesized using Ga flux and characterized by single-crystal X-ray diffraction. Ce₂PdGa₁₀ adopts a tetragonal structure in the I₄/mmm space group and is isostructural to Ce₂NiGa₁₀. Lattice parameters are , , , and Z=2. The compound is metallic (dρ/dT>0), with the resistance decreasing roughly linearly with temperature from 300 to 175 K. The magnetic susceptibility of Ce₂PdGa₁₀ is consistent with local-moment paramagnetism and no long-range magnetic ordering occurs down to 2 K. A large positive magnetoresistance over 200% is observed at 2 K for fields of 9 T. In this paper, we present the structure and physical properties of Ce₂PdGa₁₀ and compared them to CePdGa₆.