Synthesis and crystal structure of the low-temperature modification of lithium potassium zinc diphosphate LiKZnP2O7

A new polymorphic modification, α-LiKZnP₂O₇, has been synthesized, which is a low-temperature modification of the LiKZnP₂O₇ compound. The crystal structure is determined by the Rietveld method from the X-ray powder diffraction data. The compound crystallizes in the monoclinic system (space group Pc, a = 12.3621(3) Å, b = 5.0655(1) Å, c = 10.2365(3) Å, β = 90.88(1)°, Z = 2) and has a framework structure similar to that of the high-temperature β phase. The framework is formed by the diphosphate groups and the oxygen tetrahedra of the zinc and lithium atoms, which statistically uniformly occupy equivalent positions in the structure.     

Synthesis of iron aluminates and a new modification of aluminum oxide under shock waves from explosives (Review)

The results of an x-ray diffraction investigation of iron aluminate with unit cell parameter a = 8.090(4) Å, cation-defective iron aluminate Fe_0.5Al_2.23O₄ with a = 8.002 Å, and a new modification of aluminum oxide synthesized under shock waves from explosives containing aluminum are presented. Aluminum oxide can crystallize in the hexagonal system in a primitive lattice with a = 9.151(1) Å, c = 7.945(2) Å, V = 576 ų or in a tetragonal system in a primitive lattice with one-half the volume — a = 7.941(2) Å, c = 4.575(1) Å, V = 288 ų.     

Solid-phase synthesis and characterization of rare-earth chromates

Simple chromates(V) MCrO₄ (M = Sc, Y, Gd, Er, or Yb) and chromate(V) vanadates Gd(CrO₄) _x (VO₄)_{1 ? x} have been synthesized by a solid-phase method. All compounds crystallize in the xenotime-type structure, space group I4₁/amd, Z = 4. The unit cell parameters have been calculated as follows: for GdCrO₄, a = 7.209(5) Å, c = 6.318(4) Å; for ErCrO₄, a = 7.088(2) Å, c = 6.231(1) Å; for YbCrO₄, a = 7.034(1) Å, c = 6.205(2) Å; for YCrO₄, a = 7.108(3) Å, c = 6.254(3) Å; and for ScCrO₄, a = 7.012(2) Å, c = 6.188(2) Å. Symmetry D _2d , established for the CrO₄ tetrahedron during the Rietveld structure refinement, is verified by IR spectroscopy. The MCrO₄ simple chromates are paramagnets; their magnetic moments range from 1.7 to 8.1 μ _B .     

Synthesis and crystal structure of the low-temperature modification of Li<Subscript>12</Subscript>Zn<Subscript>4</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>5</Subscript>

The crystal structure of a low-temperature modification of the Li₁₂Zn₄(P₂O₇)₅ compound has been determined by full-profile analysis from the X-ray powder diffraction data. The compound crystallizes in the monoclinic crystal system (a = 5.130(1) Å, b = 13.454(1) Å, c = 8.205(1) Å, β = 90.36(1)°, space group P2₁/n, Z = 4) and has a framework structure in which the zinc and lithium atoms statistically occupy equivalent positions.     

A solvothermal synthesis of a novel 1D ladder-like (NH3CH2CH2NH3)AgAsS4 containing N–H⋯S hydrogen bonding

A one-dimensional compound (NH₃CH₂CH₂NH₃)AgAsS₄ with ladder-like chains was synthesized solvothermally. This compound crystallizes in the monoclinic system, space group C2/c, with a=13.5805(8) Å, b=6.5331(3) Å, c=22.7711(9) Å, α=90°, β=106.42(3)°, γ=90°, Z=8. The rare type hydrogen bonding of N–H⋯S and electrostatic force hold the anionic chains together.     

Synthesis and crystal structure of a new oxohalide CdPb<Subscript>2</Subscript>O<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

A new compound, CdPb₂O₂Cl₂, is synthesized by the method of solid-phase reactions. The compound has monoclinic symmetry, space group C2/m, a = 12.392(8) Å, b = 3.8040(14) Å, c = 7.658(5) Å, β = 122.64(5)°, and V = 304.0(3) ų. The structure contains one symmetrically independent position of the Pb²⁺ cation coordinated by three O^2? anions (Pb²⁺-O^2? = 2.29–2.34 Å) and five Cl^? anions (Pb²⁺-Cl^? = 3.35–3.57 Å). The Cd²⁺ cation has a symmetric coordination with the formation of two bonds Cd-O = 2.15 Å and four bonds Cd-Cl = 2.73 Å. The oxygen atom is tetrahedrally coordinated by three Pb²⁺ cations and one Cd²⁺ cation, which leads to the formation of oxo-centered heterometallic OPb₃Cd tetrahedra. The tetrahedra are linked together into chains through common Pb atoms and into layered complexes due to sharing of the equatorial Cd atoms. The chlorine atoms are located above the cavities of the oxo-centered layer.     

Preparation and Crystal Structure of KFeCl3 and KFeBr3

The preparation and crystal structures of anhydrous KFeCl₃ and KFeBr₃ are described. X-ray diffraction data obtained at room temperature indicate that the two compounds belong to the orthorhombic system, space group Pnma and z = 4. Unit cell parameters are a = 8.712 Å, b = 3.845 Å, c = 14.15 Å for KFeCl₃ and a = 9.220 Å, b = 4.026 Å, c = 14.899 Å for KFeBr₃. Atomic positions were determined.     

Thermal explosion synthesis of first Te-containing layered ternary Hf2TeB MAX phase

With the new discovery of layered boride compounds M₂AB (M = Zr, Hf, Nb; A = S, Se) with the typical Cr₂AlC-type structure, MAX phases have been successfully expanded from carbides and nitrides to borides. However, only five MAX phase borides have been synthesized at present, which means that the research on MAX phase borides is still in its infancy. Therefore, the exploration of new MAX phase borides is necessary and can provide a solid basis for future research. In this paper, we describe the discovery of the first tellurium (Te)-containing layered ternary compound Hf₂TeB using combinatorial methods of thermal explosion synthesis, XRD, SEM, and HRTEM analyses. This new MAX phase crystallizes with a Cr₂AlC-type structure with the space group of P6₃/mmc, and the lattice parameters are a = 3.60475 Å, c = 13.12663 Å, respectively, and atomic positions are Hf at (1/3, 2/3, 0.57505), Te at (1/3, 2/3, 1/4), and B at (0, 0, 0).     

The synthesis and crystal structure of [M{H2B(tz*)2}2(H2O)] (M=Cu,Zn and tz*=3,5-dimethyl-1,2,4-triazole)

New ligand [KH₂B(tz^*)₂] (tz*=3,5-dimethyl-1,2,4-triazolyl) has been synthesized and the reactions of two different metal salts (copper and zinc) with the new ligand in agar gave two similar crystalline polymorphic forms: [Cu{H₂B(tz^*)₂}₂(H₂O)] (1) and [Zn{H₂B(tz^*)₂}₂(H₂O)] (2). A single crystal X-ray study revealed that the compound 1 was the monoclinic system with space group C2/c and a=8.462(3) Å, b=14.039(6) Å, c=19.991(8) Å, β=94.622(7)°, Z=4, R₁=0.0451, wR₂=0.1110. And the compound 2 was the monoclinic system with space group C2/c and a=8.4214(4) Å, b=13.8765(7) Å, c=20.2969(6) Å, β=95.615(2)°, Z=4, R₁=0.0667, wR₂=0.1375. The metal(II) ion in the complex is five-coordinated with four nitrogen atoms which come from triazolyl and one oxygen atom which come from water molecular. In both compounds, the hydrogen atoms of water molecule are connected by hydrogen bonding with N atoms of two adjacent complex molecules to form 2-D planes. The spectroscopic results are consistent with the crystallographic study.     

X-Ray Analysis of trans-9, 10-Dihydroxy-9,10-diphenyl-9,10-dihydroanthracene and Its 1:2 Molecular Complex with Methanol,and Structural Comparison with the Related 1:1 Ethanol and 1:1 1,4-Butanediol Adducts

trans-9,10-Dihydroxy-9,10-diphenyl-9,10-dihydroanthracene (2) and its 1:2 molecular complex (3) with methanol have been subjected to X-ray analysis. The crystal structure of 2 is built of discrete molecules held by π interactions between neighboring parallel phenyl rings and van der Waals forces, whereas that of 3 features virtually rhombic hydrogen-bonded (OH)₄ rings, each comprising two methanol fragments and two hydroxy groups, linking the molecular moieties into a chain-and-layer arrangement. The molecular stereochemistry, hydrogen bonding, and packing modes in these two compounds are compared with those in the 1:1 adducts of 2 with ethanol and 1,4-butanediol. Crystal data: for 2, space group P1, a = 6.814(1), b = 8.119(1), c = 9.053(1)Å, α = 103.66(1), β = 96.30(1), γ = 106.55(1)°, and Z = 1 : for 3, space group C2/c, a = 12.165(3), b = 12.484(3), c = 16.349(4)Å, β = 110.33(2)° and Z = 4. Based on observed MoKα data, the structures of 2 and 3 have been refined to R_F = 0.069 for 1139 reflections and R_F = 0.070 for 1412 reflections, respectively.     

Synthesis and crystal structure of a new modification of sodium tetrahydroxyborate NaB(OH)<Subscript>4</Subscript>

A new polymorphic modification of sodium tetrahydroxyborate NaB(OH)₄ is synthesized and its crystal structure is determined. The compound crystallizes in symmetry space group P2₁2₁2₁ with the unit cell parameters a = 5.323(5) Å, b = 9.496(5) Å, and c = 6.596(5) Å. The discrepancy factor for 511 symmetrically nonequivalent reflections is R = 0.0188. Layers that are formed by boron tetrahedra, aligned parallel to the (010) planes, and alternate with layers of sodium cations can be distinguished in the structure.     

Determination of New α-312 MAX phases of Zr3InC2 and Hf3InC2

Present work successfully synthesized two new α-312 MAX phase compounds of Zr₃InC₂ and Hf₃InC₂ using spark plasma sintering. The crystal structure and microstructure of two new compounds were characterized by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM). With typical crystal structure of MAX phase, the obvious layered features on the fracture surface of Zr₃InC₂ and Hf₃InC₂ grains were observed. The lattice parameters of these two new MAX phase compounds were confirmed as a = 3.3515(3) Å, c = 20.2515(9) Å for Zr₃InC₂, and a = 3.3370(3) Å, c = 19.9560(1) Å for Hf₃InC₂, respectively. Also, the atomic positions of Zr₃InC₂ and Hf₃InC₂ were determined as M1 at (0, 0, 0), M2 at (1/3, 2/3, 0.12774[Zr]/0.12455[Hf]), In at (0, 0, 1/4), and C at (1/3, 2/3, 0.57087[Zr]/0.54894[Hf]). Two new sets of XRD patterns of Zr₃InC₂ and Hf₃InC₂ were collected.     

A misunderstood member of the nagelschmidtite family unveiled: structure of Ca5Na2(PO4)4 from X-ray powder diffraction data

During the development of procedures to synthesize carbonate hydroxyapatite with properties resembling those of biological material, a new phase was found to form after high temperature treatments in the presence of sodium. The compound was isolated and analytically characterized, leading to its identification as Ca₅Na₂(PO₄)₄: an analogous Ca–Na phosphate was previously described, but with rather poor diffraction data and uncertain stoichiometry. Accurate XRD powder patterns revealed a hexagonal cell, space group P6₃mc (186), a=10.64 Å, c=21.71 Å, Z=6, ρ=2.93 g/cm³, with the a axis double and the c axis triple those of the subcell typical of α-phases in the well-known system A₂XO₄ (or ABXO₄). The complete structural determination was carried out and the relevant aspects and properties discussed.     

Model bulk Mo–V–Te–O catalysts for selective oxidation of propane to acrylic acid

The crystal structures and chemical compositions of the M1 and M2 phases proposed as active and selective in propane oxidation to acrylic acid over the bulk mixed Mo–V–Te–O catalysts were investigated by the transmission electron microscopy, coupled with energy dispersive analysis of X-rays. The results revealed that the crystal structure of the M1 phase is orthorhombic with space group Pbca, lattice parameters a=21.25 Å, b=27.14 Å, c=4.03 Å and composition Mo_0.64V_0.32Te_0.1O_3.05 (Mo/V ∼2), whereas M2 is hexagonal with space group P6mm, lattice parameters a=7.10 Å, c=4.05 Å and composition Mo_1.79V_1.85Te_0.1O_11.36 (Mo/V ∼1). The M1 phase was dominant in the Mo–V–Te–O catalyst. The results obtained indicated that the bulk Mo–V–Te oxides represent a well-defined model catalytic system for the studies of the surface molecular structure-activity/selectivity relationships in propane oxidation to acrylic acid.     

SHS of single crystals in the B-C-Mg system: Crystal structure of new modification of B25C4Mg1.42 = [B12]2[CBC][C2]Mg1.42

A new modification of B₂₅C₄Mg_1.42, [B₁₂]₂[CBC][C₂]Mg_1.42, was prepared by magnesiothermic SHS and characterized by XRD. This compound was found to have the following crystallographic parameters: a = 9.626(1), b = 11.329(1), c = 8.966(1) Å, β = 105.80(3)°, V = 940.8(2) ų, space group P2₁/b, Z = 4, R = 0.032. SHS-produced crystals exhibited high acid resistance and hardness and can be recommended as a starting compound for synthesis of other modifications of carboboride.     

One-pot template synthesis and crystal structure of two new polyaza copper(II) complexes

A new 14-membered hexazamacrocyclic copper(II) complex [Cu(H₂L¹)](ClO₄)₄(L¹=1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been prepared by the one-pot reaction of ethylenediamine and formaldehyde in the presence of the Cu(II) ion. The crystal structure of [Cu(H₂L¹)](ClO₄)₄ was determined by X-ray diffraction. It crystallizes in the triclinic space group P−1 with a=12.118(2) Å, b=12.438(2) Å, c=12.466(2) Å, α=102.26(1)°, β=112.82(1)°, γ=111.51(1)°, and Z=2. The coordination geometry around the copper(II) ions is axially elongated octahedral with four nitrogen atoms of the macrocycle [Cu–N 2.012(7) Å for Cu(1) and 2.013(6) Å for Cu(2), average value] and two oxygen atoms of two ClO₄⁻ anions [Cu–O=2.550 Å for Cu(1) and 2.601(6) Å for Cu(2)]. [CuL²](ClO₄)₂(L²=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3,3,2]decane) with a novel tetraazabicyclic ligand was obtained from the same reaction system as an additional product. Crystal structure of [CuL²](ClO₄)₂: monoclinic space group Cc, a=16.393(3) Å, b=8.8640(18) Å, c= 13.085(3) Å, β=105.01(3)°, and Z=4.     

Remarks on the La2O3Li2O binary system between 750° and 1000°C

The La₂O₃Li₂O binary system has been re-examinated between 750° and 1000°C where LaLiO₂ occurs as the only binary compound. It is characterized by a monoclinic cell (a₀ = 5.88 Å; b₀ = 6.22 Å; c₀ = 5.84 Å; β = 102.53°) and is ismorphous with α-EuLiO₂. Any orthorhombic polymorph of this compound is excluded between 750° to 1000°C. Moreover, the cubic phase (a₀ = 12.22 Å) reported by previous researchers and said to have composition close to LaLiO₂ formula, actually belongs to the LaPtLiO s system. It has a variable composition: LaPt_xLi_1?xO_2+1.5x ($\text{x}\text{= 0.14}\text{0.25}$) and its lattice parameter varies from 12.215 Å (x = 0.14) to 2.284 Å (x = 0.25). An isomorphous ternary cubic phase, in which titanium replaces platinum, has also been prepared and the lattice parameter of the LaTi_0.16Li_0.84O_2.24 compositions is 12.21 Å.     

Perovskite-type MgCNi<Subscript>3</Subscript> superconductors as prepared by combined sintering-ETE process and SHS reaction: Structural and superconducting properties

Complete conversion of the elements into the Perovskite-type MgCNi₃ compound has been achieved in the following two-stage process: (1) isothermal treatment (sintering) of starting powder compacts and (2) their subsequent electrothermal explosion (ETE) under uniaxial pressure. For comparison, similar reaction was also performed by mere sintering and by SHS. The bulk anti-perovskite MgCNi₃ superconductor was prepared from Mg-C-3Ni powder compacts. Isothermal treatments failed in the formation of the perovskite-type compound as a sole product. The hexagonal MgCNi₃ phase obtained by combined sintering-ETE route was found to have the lattice constants a = 3.0845 Å and c = 3.5259Å. The grains of the MgCNi₃ obtained by sintering-ETE process are fine, well compacted, and more homogenous than those prepared by sintering or SHS. The structure of materials was characterized by XRD, SEM, and EDS. The superconducting properties were detected using the temperature dependence of magnetization M as measured in ZFC and FC experiments at H = 15 Oe. For our MgCNi₃, the superconducting transition temperature T _c is around 7 K.     

Synthesis of new lead-containing MAX phases of Zr3PbC2 and Hf3PbC2

In this work, two new 312 MAX phases of Zr₃PbC₂ and Hf₃PbC₂ were successfully synthesized by spark plasma sintering. It is the first discovery of lead-containing 312 MAX phases, which together with M₂PbC (M = Ti, Zr, Hf) form the lead-containing MAX phase family. Considering the extremely low electrical conductivity of Hf₂PbC, these two new compounds are of great research value. Based on the Rietveld refinement results, their lattice parameters and atomic positions were well determined, as a = 3.3771(5) Å, c = 20.0070(9) Å for Zr₃PbC₂ and a = 3.3357(1) Å, c = 19.7659(8) Å for Hf₃PbC₂, where M atoms are located at (0, 0, 0) and (1/3, 2/3, 0.1258(6)[Zr]; 0.1255(2)[Hf]), Pb atoms are located at (0, 0, 1/4), and C atoms are located at (1/3, 2/3, 0.0663(2)[Zr]; 0.0641(3)[Hf]), respectively. Additionally, the typical laminar microstructure of Zr₃PbC₂ and Hf₃PbC₂ grains was observed.     

Multinuclear Metal Carbonyl Alkoxide and Aryloxide Derivatives as Models for Metal Carbonyls Adsorbed on Metal Oxide Supports

The synthesis and characterization of two tungsten carbonyl dimers containing bridging alkoxide or aryloxide ligands are described. The crystal and molecular structures of [PPN]₂[W₂(CO)₈(OCH₂CF₃)₂], 1, and [Et₄N]₃[W₂(CO)₆-(OPh)₃]-CH₃CN, 2 , are reported and compared with the structures of tetranuclear tungsten derivatives previously described. The dimer 1 crystalizes in the triclinic space group P 1 with unit cell parameters a = 13.460(11) Å, b = 12.318(5) Å, c = 13.842(10) Å, α = 82.73(5)°, β = 59.11(5)°, γ= 80.09(5)°, V = 1938(2) ų, and Z = 1. The complex 2 crystalizes in the monoclinic space group P2₁/n with unit cell parameters a = 11.954(2) Å, b = 19.359(4) Å, c = 26.462(5) Å, β = 102.50(16)°, V = 5979(2) ų, Z = 4. Molecular modeling software was utilized to construct a tetranuclear derivative from 1 similar to the structurally characterized [W(CO)₃OH]₄₋⁴ tetramer. The two tetramers were found to possess similar molecular parameters. This supports the contention that dimers of type 1 are the precursors of the tetramers. Comparisons of the tungsten alkoxides and aryloxides with the behavior of W(CO)₆ on γ-alumina are provided.