Neutron diffraction study and magnetotransport properties of stoichiometric CaMoO3 perovskite prepared by a soft-chemistry route

Polycrystalline CaMoO₃ perovskite has been prepared by soft-chemistry procedures, followed by controlled annealing under reducing conditions (H₂/N₂ flow). The crystal structure, studied from neutron powder diffraction data, can be described in an orthorhombic unit cell, space group Pbnm (No. 62). The lattice parameters were a=5.4510(1) Å, b=5.5821(1) Å and c=7.7803(2) Å. In the perovskite network the MoO₆ octahedra are tilted by 13.5° in order to optimize the Ca-O bond lengths; the tilting scheme corresponds to a GdFeO₃-like superstructure. The perovskite is fully oxygen stoichiometric, as demonstrated from the refinement of the oxygen occupancy factors. Resistivity and transport measurements indicated that CaMoO₃ behaves as a metal; at low temperatures (5 K) a small positive magnetoresistance is observed, reaching a maximum value of 1.4% at 9 T. The magnetic susceptibility is predominantly Pauli paramagnetic-like, although a non-negligible temperature-dependent component due to isolated Mo⁴⁺ spins is patent at low temperatures.     

Crystal structure and electronic properties of the new compounds U3Co12−xX4 with X=Si, Ge

The new compounds U₃Co_12−xX₄ with X=Si, Ge were prepared by direct solidification of the corresponding liquid phase, followed by subsequent annealing at 1173 K. Single crystal X-ray diffraction carried out at room temperature showed that they crystallize with the hexagonal space group P6₃/mmc (no.194) and the unit-cell parameters a=8.130(5), c=8.537(5) Å and a=8.256(1), c=8.608(1) Å for the silicide and germanide, respectively. Their crystal structure derives from the EuMg_5.2 structure type, and is closely related to the Sc₃Ni₁₁Si₄ and Gd₃Ru_4−xAl_12+x types. For the present compounds, no substitution mechanisms have been observed, the partial occupancy of one Co site results from the presence of vacancies, only. The homogeneity ranges, evaluated by energy dispersive spectroscopy analysis, extend from x=0.0(2) to 0.3(2) and from x=0.0(2) to 1.0(2) for U₃Co_12−xSi₄ and U₃Co_12−xGe₄, respectively. The electronic properties of both compounds were investigated by means of DC magnetic susceptibility and DC electrical resistivity measurements. The U₃Co_12−xX₄ compounds are both Pauli paramagnets with their electrical resistivity best described as poor metallic or dirty metallic behavior.     

Binary Compounds of Rhodium and Zinc: RhZn,Rh2Zn11, and RhZn13

The title compounds were prepared by reaction of the elements at elevated temperatures in sealed silica tubes. Single crystals of RhZn and RhZn₁₃ were obtained by slow cooling of samples with a high zinc content after dissolving the zinc‐rich matrix in hydrochloric acid. Their crystal structures were determined from single‐crystal X‐ray diffractometer data. RhZn has a CsCl type structure: Pm3m, a = 300.9(1) pm. RhZn₁₃ has a CoZn₁₃ type structure: C2/m, a = 1090.8(2) pm, b = 753.7(2) pm, c = 512.7(1) pm, β = 101.02(2)°. The structure of Rh₂Zn₁₁ is isotypic with Cu₅Zn₈, the γ‐brass structure. It was refined from X‐ray diffractometer powder data: I43m, a = 909.1(1) pm. In these structures all atoms have high coordination numbers. The structure of RhZn₁₃ contains relatively large unoccupied voids. It is suggested that they accommodate nonbonding electrons. Electrical conductivity measurements of Rh₂Zn₁₁ and RhZn₁₃ indicate metallic behavior, however, with an unexpectedly high resistivity for Rh₂Zn₁₁. The expected Pauli paramagnetism of these compounds is overcompensated by the core diamagnetism, suggesting a low density of states at the Fermi level especially for Rh₂Zn₁₁. This correlates with the high electrical resistivity of this compound.     

CaRhIn with TiNiSi Type Structure and CaTIn2 (T = Rh,Ir) with a New Filled Version of the Zintl Phase CaIn2

CaRhIn, CaRhIn₂, and CaIrIn₂ were synthesized by reacting the elements in glassy carbon crucibles under an argon atmosphere in a high‐frequency furnace. CaRhIn adopts the TiNiSi structure: Pnma, a = 730.0(4) pm, b = 433.1(2) pm, c = 828.8(4) pm, wR2 = 0.0707, 630 F² values, 20 variables. The CaRhIn structure consists of strongly puckered Rh₃In₃ hexagons with Rh–In distances ranging from 273 to 276 pm. Due to the strong puckering each rhodium atom has a distorted tetrahedral indium environment. The calcium atoms fill the channels within the three‐dimensional [RhIn] polyanion. CaRhIn₂ and CaIrIn₂ crystallize with a new structure type: Pnma, a = 1586.2(3) pm, b = 781.4(2) pm, c = 570.9(1) pm, wR2 = 0.0385, 1699 F² values, 44 variables for CaRhIn₂, and Pnma, a = 1588.7(3) pm, b = 780.8(1) pm, c = 574.0(1) pm, wR2 = 0.0475, 1661 F² values, 44 variables for CaIrIn₂. The structures of CaRhIn₂ and CaIrIn₂ can be described as an orthorhombically distorted rhodium respectively iridium filled CaIn₂. The motif of transition metal filling is similar to that found in MgCuAl₂ type compounds CaTIn₂ (T = Pd, Pt, Au) and SrTIn₂ (T = Rh, Pd, Ir, Pt), but constitute a different tiling. Semi‐empirical band structure calculations for CaRhIn and CaRhIn₂ reveal strong bonding In–In and Rh–In but weaker Ca–Rh and Ca–In interactions. Magnetic susceptibility and resistivity measurements of compact polycrystalline samples of CaRhIn₂ indicate weak Pauli paramagnetism and metallic conductivity with a room temperature value for the specific resistivity of 230 ± 50 μΩcm.     

Structural properties of VP1−x As x ; 0.00≦x≦1.00

The VP-VAs system has been studied by powder diffraction and magnetic susceptibility measurements. Three regions of solid solubility, separated by two phase regions, are found for VP_1–x As _x as function of composition (x). An NiAs type phase prevails for 0.00x0.07±0.02, a hexagonal phase of unknown crystal structure for 0.17±0.02x0.63±0.02 and an MnP type phase for 0.83±0.02x1.00. No phase transition is observed between 10 and 1 300 K. The various VP_1–x As _x phases exhibitPauli paramagnetism.Dedicated to Professor Dr.Kurt L. Komarek on his 60th birthday June 23, 1986.     

Ce掺杂对MoSn催化剂选择氧化二甲醚制备甲酸甲酯性能的影响

采用无沉淀剂一步水热法合成了不同含量Ce掺杂的MoSn催化剂，考察了Ce的掺杂量对其二甲醚（DME）选择氧化催化性能的影响。结果表明，当Ce含量为0.5%时，MoSn催化剂的活性最高，在130℃下DME的转化率达11.8%，MF的选择性为92.2%。采用氮吸附、XRD、NH₃-TPD、CO₂-TPD、H₂-TPR、XPS和in situ-IR等表征技术对催化剂进行了表面性质和结构分析，发现Ce的掺杂虽然没有从根本上改变MoSn催化剂的结构，但明显提高了MoSn催化剂中五价钼的含量。     

The Molybdenum(0) Complex 〔Et_4N〕_2〔Mo_2(CO)_6(pys)_2〕(pys=Pyridine-2-thiolato)

１ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｒｅｓｅａｒｃｈｏｎａｓｅｒｉｅｓｏｆｄｉｎｕｃｌｅａｒｍｏｌｙｂｄｅｎｕｍ（０）ｃａｒｂｏｎｙｌｃｏｍｐｌｅｘｅｓｃｏｎｔａｉｎ ｉｎｇｔｈｉｏｌａｔｏ ｂｒｉｄｇｅｓｈａｓｌｅｄｔｏｔｈｅｃｏｎｃｌｕｓｉｏｎ...     

The Reaction of Molybdenum with 2,3-Dihydroxynaphthalene

[H2N（CH2）3NH312[MoO2（C10H6O2）2] （1） was synthesized by the 2,3-dihydroxynaphthalene in the mixed solvent of CH3OH, CH3CN reaction of （n-Bu4N）4[Mo8O26] with and 1,3-propanediarnine. （C5HllN2）2- [HeN（CH2）3NH2][MoO2（CloH6O2）2] （2） was obtained by the reaction of Na2MoO4.2H20 with 2,3-dihydroxynaphthalene in the same solvent above. Both of the complexes possess complex anion [Mo（VI）O2（OC10H6O）2]^2- which shows pseudo-octahedrally coordinated fashion, while the counterions are two protonated 1,3-propanediamine in complex 1 and （CsH11N2）^＋ in complex 2. （C5H11N2）＋ is the byproduct of reaction 2, which results from combination of acetonitrile with 1,3-propanediamine. Packing diagrams of the two complexes are also different. There is anti-parallel-aligned-double-meso-bilayer unit in complex 1. However there are four chiral anions arranged in anticlockwise orientation in complex 2.     

The Molybdenum(0) Complex [Et4N]2[Mo2(CO)6(pys)2](pys=Pyridine-2-thiolato)

The title compound tetraethylammonium hexacarbonylbis(μ-pyridine-2-thiolato-S∶S) dimolybdenum [Et4N]2[Mo2(CO)6(pys)2] crystallizes in the monoclinic, space group, P21/c with a=13.217(2), b=21.648(2), c=27.193(6)(), β=82.52(2)°, V=7714.6()3, Z=8, Mr=840.77, Dc=1.45 g/cm3, μ=7.8 cm-1, R=0.038 and Rw=0.040 for 6082 reflections with I≥3σ(I). X-ray crystal structure study reveals that the asymmetric unit of the title compound is comprised of two independent formulations of the molecular formula. Each dianion has approximate C2 symmetry and the dimetallic Mo2S2 core adopts a "butterfly" conformation with a dihedral angle between the halves of 139.3(1)° for the first independent anion and 142.8(1)° for the second one. The two pyridine rings lie on the same side of the molecule in a cis arrangement and the Mo...Mo separations are 3.76(1) and 3.838(1)().     

Neutron diffraction study, magnetism and magnetotransport of stoichiometric CaVO3 perovskite with positive magnetoresistance

A stoichiometric calcium vanadium (IV) oxide with formula CaVO₃ has been prepared by soft-chemistry procedures, followed by annealing under reducing conditions (H₂/N₂ flow). This material has been studied by X-ray and neutron powder diffraction (NPD), thermal analysis, magnetic and magnetotransport measurements. CaVO_3.0 perovskite crystallizes in the orthorhombic Pbnm (No. 57) space group, with the GdFeO₃-type structure. The unit-cell parameters are , and . In this distorted perovskite the VO₆ octahedra are tilted by 10.1° in order to optimize the Ca-O bond-lengths. A bond valence study from NPD data confirms the tetravalent oxidation state for V cations. The perovskite is fully oxygen stoichiometric, as demonstrated from thermal analysis and the refinement of the oxygen occupancy factors. The magnetic susceptibility is predominantly Pauli paramagnetic-like, although a non-negligible temperature-dependent component due to isolated V⁴⁺ spins is patent at low temperatures. The transport measurements show a metallic behavior between 2 and 300 K; at low temperatures a positive magnetoresistance as large as 14% for H=9 T is interpreted as the result of quantum interference effects.     

Structure of Molybdenum Complex of Benzothiazole－2－thiolate（η~5－C_5H_5）Mo（CO）_2（C_7H_4NS_2）

ＳｔｒｕｃｔｕｒｅｏｆＭｏｌｙｂｄｅｎｕｍＣｏｍｐｌｅｘｏｆＢｅｎｚｏｔｈｉａｚｏｌｅ－２－ｔｈｉｏｌａｔｅ（η~５－Ｃ_５Ｈ_５）Ｍｏ（ＣＯ）_２（Ｃ_７Ｈ_４ＮＳ_２）ＣｈｅｎｇＧｕｏ－Ｂａｏ~ａ；ＷｕＱｉａｎｇ－Ｊｉｎ~ｂ；ＨｕａｎｇＸｉａｏ－Ｙｉｎｇ~...     

Crystal structure of the Molybdenum(V) Diphosphate KMoP2O8 isotypic with KNbP2O8

A new molybdenum(V) diphosphate KMoP₂O₈ has been isolated. The single crystal X-ray diffraction study of this phase has shown that it is isotypic with KNbP₂O₈. It crystallizes in the P2₁/n space group a = 5.0862(4), b = 11.720(1), c = 11.486(1) Å, β = 90.91(1)°. The structure of this phase is compared with those of other molybdenum(V) diphosphates. This tunnel structure is described in terms of [MP₂O₈]₈∞ ribbons running along ā, showing close relationships with the titanophosphate NaTiP₂O₇. The existence of one free apex for each MoO₆ octahedron and each P₂O₇ group, respectively, is emphasized, allowing a great flexibility of the structure.     

Synthesis and Crystal Structure of Cubane—typeMolybdenum Cluster ComplexMo4S4（DTP）4[μ—SOP（OEt）2]2

1 INTRODUCTION Trinuclear molybdenum complexes with Mo3(3-S)(-O)n(-S)3n (n = 0~3) cores have been extensively studied on their diversified reactions towards various organic ligands and many metals. Many derivatives with Mo3S4 core have been rationally synthesized from the cation precursor [Mo3S4(H2O)9]4+ and its neutral derivative Mo3(3-S)(-S)3(DTP)4(H2O)[1]. However, due to their structural lability, complexes with Mo3(3-S)(-O)n(-S)3n (n = 1~3) cores have been reported limitedl…     

Synthesis and Characterization of Ethylenediammonium Molybdenum Thiocomplex [H3NCH2CH2NH3][Mo3S13]

An organo‐spaced molybdenum thiocomplex [ H₃NCH₂CH₂‐NH₃][Mo₃S₁₃] has been synthesized under hydrothermal condition and the structure of the compound was determined by single‐crystal X‐ray diffraction. The title compound crystallizes in the monoclinic space group C2/c with a = 1.81157 (18), b = 1.04549(9), c = 2.04892(19) nm, β= 107.184 (2)°, Z = 8 and V = 3.7074(6) nm³. The inorganic part of the compound consists of a Mo₃ triangle capped by an apical μ₃‐sulfur atom, with each Mo atom being also coordinated to one terminal disulfur ligand and two bridging disulfur ligands. The negative charges on the inorganic cluster are balanced by the diprotonated ethylenediamine cations [ H₃NCH₂CH₂‐NH₃]²⁺ located in the space between the clusters.     

Crystal Structure of 2-(4-Fluorophenylamino)-2-thiomethyl acetophenone

1mThODUCTIONThioacetalshavebeenwellstudied,becauseoftheirapplicationsinorganicsyn-thesist1i.However,aketohemithioacetalshaveseldombeeninvestigated.Inthispa-Per,wediscussedthecrystalstructureofthetitlecompoundsynthesizedbythereac-tionofabenzoylhemithioacetal(2-hydroxy-2-thiomethylacetoPhenone)and4-fluthroaniline.Sinceknowledgeofthemolecularandcrystalstructureofthetitlecom-PoundwasconsideredusefulforunderstandingthemechanismofthereactionandchemicalproPertiesofaketohemithioacetal,theX-raycr…     

Complexation of Molybdenum（Ⅵ） with R－and S－malic Acid， The Crystal Structure of（NH_4）_4［（MoO_2）_4O_3（R－mal）_2］·6H_2O

ＣｏｍｐｌｅｘａｔｉｏｎｏｆＭｏｌｙｂｄｅｎｕｍ（Ⅵ）ｗｉｔｈＲ－ａｎｄＳ－ｍａｌｉｃＡｃｉｄ，ＴｈｅＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆ（ＮＨ_４）_４［（ＭｏＯ_２）_４Ｏ_３（Ｒ－ｍａｌ）_２］·６Ｈ_２ＯＺｈｏｕＺｈａｏ－Ｈｕｉ；ＹａｎＷｅｎ－Ｂｉ?..     

二维层状结构十钒酸盐[K(H2O)2Ni(H2O)6]2[V10O28]的合成及性质(英)

A novel heteropoly compound, containing two kinds of coordinated cations, [K(H₂O)₂Ni(H₂O)₆]₂[V₁₀O₂₈], has been synthesized through routine process and characterized by elemental analyses, IR, ⁵¹V NMR and single crystal X-ray diffraction. It crystallizes in the triclinic system, space group P1 with a=0.87382(17) nm, b=1.075 4(2) nm, c=1.111 1(2) nm, α=65.10(3)°, β=75.01(3)°, γ=70.63(3)°, V=0.884 8(3) nm³ and Z=1. The X-ray analysis reveals that the two kinds of coordinated cations are linked by three shared coordinated water molecules, and K⁺ cations coordinate with ten oxygen atoms: five of which come from V₁₀O₂₈^6- anion, the other five from water molecules. The title compound exhibits extended 2D array building up of V₁₀O₂₈^6- groups connected by ten-coordinated K⁺ cations. The hexahydrated nickel cations Ni(H₂O)₆²⁺ lie in neat apposition to three adjacent V₁₀O₂₈^6- clusters. CSD: 413271.     

Structure of GdMg（BO2）5 Crystal

1 INTRODUCTION With the development of diode-pumped solid-sta- te lasers, the research to find more efficient materials for these lasers is gaining more importance. The luminescent materials host LnMgB5O10 may become potential solid-state laser materials[1, 2]. Nd3 -doped GdMg(BO2)5 as a potential diode-pumped laser crystal has been grown in our lab and characterized by a very strong absorption at near 808 nm and intense emission. Although the previous work repor- ted LaMg(BO2)5 with…     

Crystal Structure,Magnetism, 89Y Solid State NMR,and 121Sb Mössbauer Spectroscopic Investigations of YIrSb

The ternary antimonide YIrSb was synthesized from the binary precursor YIr and elemental antimony by a diffusion controlled solid‐state reaction. Single crystals were obtained by a flux technique with elemental bismuth as an inert solvent. The YIrSb structure (TiNiSi type, space group Pnma) was refined from single‐crystal X‐ray diffractometer data: a = 711.06(9), b = 447.74(5), c = 784.20(8) pm, wR₂ = 0.0455, 535 F² values, 20 variables. ⁸⁹Y solid state MAS NMR and ¹²¹Sb Mössbauer spectra show single resonance lines in agreement with single‐crystal X‐ray data. YIrSb is a Pauli paramagnet.     

Hydrothermal Synthesis and Structure of a New Molybdenum Phosphate: (NH_3CH_2CH_2NH_3)_(2.5)[Mo_5O_(15)(PO_4) (HPO_4)]·7.5H_2O

1 INTRODUCTION A new class of materials of metal oxide clusters based on anionic molybdenum phosphate frameworks has received much attention as a consequence of their potential applications in catalysis and materials science [1]. As a result, some molybdenum phosphates have been studied [2,3]. Recently we have studied the structure of NaPMO material[4] and the spectrum of multicomponent compound with Keggin struc- ture [5]. Here we report the synthesis and crystal structure of a new…