Tantalcluster in oxidischer Matrix – Synthese und Strukturen der gemischtvalenten Oxotantalate M2–δTa15O32 (M = K,Rb (δ = 0); M = Sr (δ = 0.15), Ba (δ = 0.12))

Tantalum Cluster in an Oxidic Matrix – Synthesis and Structures of Mixed-Valence Oxotantalates M_2–δTa₁₅O₃₂ (M = K, Rb (δ = 0); M = Sr (δ = 0.15), Ba (δ = 0.12)) The mixed-valent oxides Sr_1.85Ta₁₅O₃₂ ( 1 ), Ba_1.88Ta₁₅O₃₂ ( 2 ), K₂Ta₁₅O₃₂ ( 3 ), Rb₂Ta₁₅O₃₂ ( 4 ) were prepared from appropriate mixtures of Ta₂O₅, tantalum and the corresponding carbonate at 1520–1670 K in sealed tantalum tubes. According to X-ray single crystal structure analyses the oxides crystallize in the space group R3¯, Z = 1. The lattice parameters in the hexagonal setting are a = 777.36(11), c = 3516.2(7) pm for 1 , a = 778.87(11), c = 3548.1(7) pm for 2 , a = 780.7(2), c = 3573.1(11) pm for 3 , and a = 781.90(11), c = 3593.0(7) pm for 4 . The oxide ions form a defect dense packing with the layer sequence chhhh. Anti-cuboctahedral sites are completely occupied by the alkali metal cations. The alkaline earth cations occupy 92 to 94% of such sites; they are displaced from the centres. Smaller voids are located in the centres of the cuboctahedral Ta₆O₁₂ clusters forming the characteristic structural unit of these low-valent oxotantalates. In case of 3 and 4 the clusters have 13 electrons, in case of 1 and 2 they have close to 15 electrons available for Ta–Ta-bonding. Moreover, the structures of the alkali and alkaline earth metal compounds differ notably with respect to the spectrum of Ta–O and Ta–Ta distances in the Ta₃O₁₃ octahedra triples forming another characteristic structural unit for these oxides. Such differences are traced back to distinct local charge balances for the uni- and divalent cations. The oxides 2 , 3 are semiconductors with band gaps ranging from 130 to 360 meV.     

Die Kristallstruktur der Hexagonalen Verbindungen BaMeIISbO9. II. Ba3CuSb2O9

Crystal Structure of the Hexagonal Compounds Ba^II₃Me^IISb^v₂O₉. II. Ba₃CuSb₂O₉ The crystal structure of the compound Ba₃CuSb₂O₉ was determined from single crystal X-ray diffraction data and refined down to R = 0.03. Ba₃CuSb₂O₉ crystallizes in the hexagonal space group P6₃mc (C) with a = b = 5.809 Å, C = 14.321 Å and Z = 2. The structure can be described by close–packed BaO₃ layers in the sequence cchcchcch…?(hex. BaTiO₃ type). Groups of two octahedra with common faces are connected by SbO₆ octahedra via common corners. They are occupied alternately by Cu and Sb. In agreement with the EPR spectra the CuO₆-octahedra present no static Jahn-Teller distortion at room temperature. However the thermal ellipsoids of the oxygen atoms indicate the presence of adynamic Jahn-Teller-effect.     

The infrared spectra of pyridine N-oxide complexes of transition metal perchlorates in relation to their structures

The infrared spectra of the complexes [M(pyO)₆](ClO₄)₂ (pyO = pyridine N-oxide; M = Mn, Fe, Co, Ni, Zn) are discussed. Assignments of v(M-O) and other significant vibrations are based on the band shifts induced by deuteration of the heterocyclic ring and the effects of metal ion substitution. Earlier spectroscopic evidence suggesting distortion from regular octahedral site symmetry is discounted by the far-infrared spectra. In agreement with recent crystallographic evidence for O_h site symmetry in these complexes, one infrared-active v(M-O) band is expected and observed. The effects on the spectra of structural distortion in the 6-coordinate Cu^II complex [Cu(pyO)₆](ClO₄)₂, reduced coordination number in the 4-coordinate complex [Cu(pyO)₄](C1O₄)₂, and increased cationic charge in the Ga^III complex [Ga(pyO)₆](C1O₄)₃are discussed.     

Catalytic properties of manganites in the oxidation of CO and hydrocarbon

Manganites with a spinel structure MMn₂O₄ (M = Co, Cu, Zn, Mo) and M¹ _0.5M² _0.5 Mn₂O₄ (M = Co, Cu, Zn, Mg) have been synthesized and tested in the catalytic oxidation of CO, C₃H₆, and ethylbenzene. The dependence of the catalytic activity of the manganites on the nature of the cation has been established. The spinels containing transition metal ions (Cu, Co) are more active. A relation between catalytic and adsorption properties of manganites has been established. The participation of the lattice oxygen in the oxidation of CO to CO₂ has been found. The mechanism of the oxidation is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 11, pp, 2686–2669. November, 1996.     

Crystal structure of a cobalt oxide LuBaCo<Subscript>4</Subscript>O<Subscript>7</Subscript>

Crystals of LuBaCo₄O_7+δ (114Lu) have been obtained by spontaneous crystallization of slowly cooled nonstoichiometric melt of the system Lu-Ba-Co-O. The crystals have been characterized by EDX microprobe and synchrotron radiation powder diffraction. Structure refinement has been carried out (automated diffractometer Bruker X8 APEX with a CCD detector, MoK _α, graphite monochromator, ?_max = 32.54°). Parameters of the hexagonal unit cell: space group P6₃ mc, a = 6.2601(1) Å c = 10.2017(3) Å V = 346.23(1) Å₃, Z = 2, d _calc = 6.331 g/cm₃. Framework structure of the wurtzite type has been refined anisotropically to R-factor 0.0174. Charge balance in the compound and geometrical matching of structural fragments are discussed.     

(NixMg1−x)10Ge3O16: A new phase with structure related to olivine and spinel

A new compound, (Ni_xMg_1−x)₁₀Ge₃O₁₆(x ⋍ 0.4−0.5), has been identified at atmospheric pressure in the NiO-MgO-GeO₂ system. Its unit cell is rhombohedral with the (hexagonal) parametersa = 5.887(1)A˚, c = 28.603(4)A˚, andZ = 3 for a phase with the Ni₄Mg₆Ge₃O₁₆ composition. A structural model has been derived from powder X-ray diffraction data: theM₁₀Ge₃O₁₆(M =Ni + Mg) structure results from a regular intergrowth of {111} layers of the spinel and rock-salt structures. It can also be described as an intergrowth of (001) olivine layers (Pnma setting) with {111} layers of a cation-deficient rock-salt structure. Due to its close relationship to both spinel and olivine, theM₁₀Ge₃O₁₆(M =Ni + Mg) structure could possibly occur at the phase boundary involved in the polymorphic olivine ⇄ spinel transformation.     

Catalytic properties of chromites with a spinel structure in the oxidation of CO and hydrocarbons and reduction of nitrogen oxides

The catalytic activity of supported chromites MCr₂O₄/-Al₂O₃ (M = Cu, Co, Mn, Zn, Mg) in the oxidation of CO, C₃H₆, and o-xylene and NO_x reduction was studied. The catalytic activity depends on the calcination temperature and cation nature. The features of the formation of the catalysts were studied by the UV-Vis diffuse reflectance and IR spectroscopies.     

A Bicapped α‐Keggin Unit‐Supported Transition Metal Complex: Hydrothermal Synthesis and Characterization of [Cu(en)2(H2O)]2[Cu(en)2]0.5[Mo8V7O42{Cu(en)2}]

A new metal‐oxo cluster supported transition metal complex, [Cu(en)₂(H₂O)]₂[Cu(en)₂]_0.5[Mo^VI₈V^IV₆V^VO₄₂{Cu(en)₂}], has been synthesized under hydrothermal conditions. Its structure was determined by single‐crystal X‐ray diffraction. The compound crystallizes in the triclinic system, space group (No. 2), a = 12.245(5), b = 12.669(5), c = 20.949(8) Å, α = 77.120(13), β = 78.107(17), γ = 65.560(14)°, V = 2860(2) ų, Z = 2. The metal‐oxo cluster contains a novel bicapped a‐Keggin structure unit and a [Cu(en)₂]²⁺ unit covalently bonded to the [Mo₈V₇O₄₂]^7? cluster.     

Structures,magnetic properties,and electronic counting rule of metals‐encapsulated cage‐like M2 Si18 (M = Ti‐Zn) clusters

The geometries, magnetic properties and stabilities of the transition metal (TM) atoms encapsulated M₂Si₁₈ (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) clusters have been systematically calculated by using the density function theory with generalized gradient approximation. Only when the doping metal atom has no more than half‐full d electronic shell, a double hexagonal prism cage‐like M₂Si₁₈ structure could form. The total moments of M₂Si₁₈ are either 0 or 2μ_B. Co₂Si₁₈ is the most stable cluster among all 3d doped M₂Si₁₈ clusters. The model of shell closure at the TM atom may be helpful to understand the stability of M₂Si₁₈ clusters. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Dimensions of the Ozonide Anion in M([18]crown‐6)O3·x NH3 with M = K (x = 2), Rb (x = 1) and Cs (x = 8)

Reaction of alkali metal ozonides (KO₃, RbO₃ and CsO₃) with [18]crown‐6 in liquid ammonia yields compounds of the composition M([18]crown‐6)O₃·x NH₃ with M = K (x = 2), Rb (x = 1) and Cs (x = 8). The large intermolecular distance between adjacent radical anions in these compounds leads to almost ideal paramagnetic behavior according to Curie's law. Discrepancies concerning the structure of the ozonide anions in the K and Cs compound compared to a former investigation on Rb([18]crown‐6)O₃·NH₃ have been resolved by means of DFT calculations and a single‐crystal structure redetermination.     

反应吸附脱硫中有序介孔Cu-ZnO-l2O3吸附剂提高其饱和硫容

目前汽柴油中的含硫化合物是造成酸雨和PM2.5的重要原因之一.随着污染的日益严重,对汽柴油的深度脱硫受到越来越多的关注.环境保护组织颁布了较为严格的法律措施,规定硫含量低于10 ppm.然而,传统的加氢脱硫工艺(HDS)很难满足在深度HDS的同时辛烷值损失较少.为了减少辛烷值损失,脱硫技术和催化剂应具有较好的选择性.因此,在FCC汽油升级的过程中,减少辛烷值损失的超深度脱硫工艺是重要研究课题之一.目前,一些新型的深度脱硫技术包括吸附脱硫、氧化脱硫和生物脱硫.其中吸附脱硫具有高选择性、低能耗等优点,而反应吸附脱硫则被广泛研究和工业化生产.常见Ni/ZnO吸附剂利用高空速控制辛烷值损失,但频繁的再生过程影响催化剂的稳定性.目前,一种新型的Cu/ZnO吸附脱硫剂用于固定床中,具有较高的脱硫活性、稳定性和高选择性.目前,铜基吸附剂面临着ZnO的饱和硫容、稳定性及活性组分Cu结焦问题.Al2O3作为稳定剂可以提高反应活性和稳定性,其中有序介孔能够提供较大的比表面积、孔径、规整的孔结构和较好的分散活性组分的能力,从而有利于分子之间的扩散.本文利用一步溶剂蒸发自组装法合成了具有有序介孔的Cu-ZnO-Al2O3吸附剂.SXRD/WXRD结果,证实合成了具有有序介孔结构的Al2O3,且添加Cu和Zn物种后,其结构并未发生改变,但当Zn的添加量达到25 wt%时,其有序介孔结构发生改变.有序介孔的Cu-ZnO-Al2O3吸附剂具有较高的比表面积、孔容及孔径,添加过量的ZnO后,其比表面积明显降低.TEM和AADF-STEM结果发现,所制Cu-ZnO-Al2O3吸附剂具有规则的介孔结构,并且Cu,Zn,Al和O分散均匀,与XRD和BET结果一致.热重结果表明,有序介孔Cu-ZnO-Al2O3吸附剂具有较好的热稳定性.通过与商业Cu-ZnO-Al2O3吸附剂进行对比,有序介孔Cu-ZnO-Al2O3吸附剂具有较高脱硫活性、饱和硫容及稳定性.     

4‐Nitro­anilinium nitrate

The crystal structure of the title compound, C₆H₇N₂O₂⁺·NO₃⁻, is built up from 4‐nitro­anilinium cations and nitrate anions. The NO₂ group is coplanar with the aryl ring, which shows significant distortion from the ideal hexagonal form. The NO₃⁻ anion is planar but shows distortion from the C_3h symmetry that is predicted by molecular orbital calculations. Two of the three O atoms of the NO₃ group are involved in hydrogen bonds as acceptors.     

Structural chemistry of Ba2CdS3, Ba2CdSe3, BaCdS2, BaCu2S2 and BaCu2Se2

The structures of all compounds were determined from three dimensional single crystal X-ray diffraction data and refined by least squares. Ba₂CdS₃ and Ba₂CdSe₃ are isostructural, Pnma, a = 8.9145(6)Å, b = 4.3356(2)Å, c = 17.2439(9)Å for the former compound and a = 9.2247Å, b = 4,4823(6)Å, c = 17.8706(11)Å for the latter, z = 4, R = 0.0751 and R = 0.0462, respectively. The compounds are isostructural with the previously reported Mn analogues and with K₂AgI₃. Cd ions are in tetrahedral environment and the tetrahedra form infinite linear chains by corner sharing. Ba ions are in 7-fold coordination in which 6 anions form a trigonal prism and 1 anion caps one of the rectangular faces. BaCdS₂, Pnma, a = 7.2781(3)Å, b = 4.1670(1)Å, c = 13.9189(6)Å, z = 4, R = 0.0685. Cd ions can be considered to have a triangular planar coordination with CdS distances of 2.47 and 2.53 Å (twice). Two additional S ions are at 2.89 and 3.22 Å to complete a triangular bipyramidal configuration. Ba is in 7-fold coordination with the anions forming a trigonal prism which is capped on one rectangular face. The compound is isostructural with BaCdO₂ and is related to the structure of BaMnS₂. BaCdSe₂ could not be prepared. BaCu₂S₂ and BaCu₂Se₂ are isostructural, Pnma, a = 9.3081(4)Å, b = 4.0612(3)Å, c = 10.4084(5)Å for the sulfide and a = 9.5944(6)Å, b = 4.2142(4)Å, c = 10.7748(8)Å for the selenide, z = 4, R = 0.0634 and 0.0373, respectively. Ba ions are in the usual 7-fold, capped hexagonal prism, coordination. However, 9 Cu ions also can be considered to form a trigonal prism with all rectangular faces capped, around Ba since the BaCu distances range from 3.24 to 3.54 Å for the sulfide and from 3.37 to 3.67 Å for the selenide. One of the Cu ions is in a very distorted tetrahedral environment and the second one is located in a more regular tetrahedral configuration of the anions. Two independent infinite chains of tetrahedra are present. They are formed by sharing of two adjacent edges of each tetrahedron and then these chains in turn are linked by corner sharing into a three-dimensional network of tetrahedra.     

Tetrastrontium dimanganese copper nonaoxide,Sr4Mn2CuO9

Single crystals of Sr₄Mn_2.09Cu_0.91O₉ have been grown by flux synthesis and the structure, closely related to the hexagonal perovskite 2H, was solved from single‐crystal X‐ray data in space group P321. The structure of Sr₄Mn₂CuO₉ is composed of chains of face‐sharing polyhedra with a sequence of two octahedra and one trigonal prism. The octahedra are filled by Mn atoms and the Cu atoms are randomly distributed at the centres of the square faces of the trigonal prism. A stacking fault is observed within one of the two chains, which can be attributed to a shifting of the chain along the c axis.     

Synthesis,Crystal Structures,and Thermolysis Studies of Heteronuclear Transition Metal Aluminum Alcoholates

Heteronuclear alcoholate complexes [M{Al(OiPr)₄}₂(bipy)] ( 2-M , M = Fe, Co, Ni, Cu, Zn) and [M{Al(OcHex)₄}₂(bipy)] ( 3-M , M = Fe, Co, Ni, Zn) are formed by adduct formation of [M{Al(OiPr)₄}₂] ( 1-M , M = Fe, Co, Ni, Cu, Zn) with 2,2'-bipyridine and transesterification reaction with cHexOAc. According to crystal structure analyses, in 2-M and 3-M the central transition metal ion M²⁺ is coordinated by two chelating Al(OR)₄^– moieties and one bipyridine ligand in an octahedral arrangement. Treating 1-Cu with 2,2'-bipyridine leads to a reduction process, whereat the intermediate [Cu{Al(OiPr)₄}(bipy)₂][Al(OiPr)₄] ( 4 ) could be structurally characterized. During conversion of the iso-propanolate ligands in 1-Cu to cyclohexanolate ligands, Cu²⁺ is reduced to Cu⁺ forming [Cu{Al(O^cHex)₄}(py)₂] ( 5 ). UV/Vis-spectra and results of thermolysis studies by TG/DTA-MS are reported.     

Preparation and crystal structure of Guanidinium Cyclododecaphosphate Telluric Acid Hydrate: [C(NH2)3]12P12O36 · 12 Te(OH)6 · 24H2O

The title compound ist the first example of an adduct between telluric acid and the twenty four membered ring anion of a cyclododecaphosphate. [C(NH₂)₃]₁₂P₁₂O₃₆ · 12 Te(OH)₆ · 24 H₂O crystallizes trigonal (rhomboedral: R3) with Z = 3 and the unit-cell dimensions a = 15.854(9), c = 51.26(2) Å in the hexagonal setting. The crystal structure was solved by direct methods and refined to a final R value of 0.031. It is characterized by a succession of three different typs of alternating layers perpendicular to the c direction. This layers are connected only by hydrogen bonds. The individual layers are built up of A: P₁₂O₃₆ anions, guanidinium cations and water of crystallisation, B: hexagonal arranged Te(OH)₆ groups and guanidinium cations and C: water of crystallization.     

Structural and electrical properties evolution in Ba1−xSrxRuO3 synthesized under high pressure

The 6H and 6M Ba_1−xSr_xRuO₃ at x?0.6 with the normal and distorted hexagonal BaTiO₃ structures were synthesized by using high-pressure and high-temperature method. It is found that the unit cell volume deviates from Vegard's law between 0.3 and 0.4 for the solid solutions due to the increasing distortion degree of crystal structure. With the increasing x, the electrical resistivity at the same temperature is increasing. With the substitution of Sr for Ba ion, the 6H BaRuO₃ transforms to a Fermi-liquid metal at x=0.25 from the primal non-Fermi-liquid metal, and then becomes a semiconductor at low temperature when x is larger than 0.4.     

Polymorphism and photoluminescence properties of K3ErSi2O7

Two polymorphs of tripotassium erbium disilicate, K₃ErSi₂O₇, were synthesized by high‐temperature flux crystal growth during the exploration of the flux technique for growing new alkali rare‐earth elements (REE) containing silicates. Their crystal structures were determined by single‐crystal X‐ray diffraction analysis. One of them (denoted 1 ) crystallizes in the space group P6₃/mmc and is isostructural with disilicates K₃LuSi₂O₇, K₃ScSi₂O₇ and K₃YSi₂O₇, while the other (denoted 2 ) crystallizes in the space group P6₃/mcm and is isostructural with disilicates K₃NdSi₂O₇, K₃REESi₂O₇ (REE = Gd–Yb), K₃YSi₂O₇, K₃(Y_0.9Dy_0.1)Si₂O₇ and K₃SmSi₂O₇. In the crystal structure of polymorph 1 , the Er cations are in an almost perfect octahedral coordination, while in the crystal structure of polymorph 2 , part of the Er cations are in a slightly distorted octahedral coordination and the other part are in an ideal trigonal prismatic coordination environment. Sharing six corners, disilicate Si₂O₇ groups in the crystal structure of polymorph 1 link six ErO₆ octahedra, forming a three‐dimensional network and nine‐coordinated potassium cations are located in its holes. In the crystal structure of polymorph 2 , the disilicate Si₂O₇ groups connect four ErO₆ octahedra, as well as one ErO₆ trigonal prism. Three differently coordinated potassium cations are situated between them. Different site symmetries of the erbium cations in the crystal structures of polymorphs 1 and 2 affect their photoluminescence properties. Only polymorph 2 exhibits luminescence. Intense narrow lines in the emission spectrum are a result of the 4f–4f transition. The green emission line at 560 nm is the result of the Er³⁺ transition ⁴S_3/2→⁴I_15/2, and the luminescence line at 690 nm is the result of a ⁴F_9/2→⁴I_15/2 transition. The crystal morphologies of the two polymorphs are similar. Crystals of polymorph 1 are in the form of a hexagonal prism in combination with a hexagonal base, while crystals of polymorph 2 contain a dihexagonal prism in combination with a hexagonal base, although poorly developed faces of the dihexagonal pyramid can also be noticed.     

Mechanism of oxygen releasing of copper ferrite in the formation of the corresponding oxygen-deficient compound

Copper ferrite is a promising material for hydrogen production through thermochemical water splitting. In this work, the cation distribution of copper ferrite and the corresponding oxygen-deficient compound of spinel structure was analyzed based on the crystal structural chemistry theory. The mechanism of oxygen releasing of CuO, Fe₂O₃, CuFe₂O₄ and metal (M=Ni, Mn or Zn) doped copper ferrite in the process of temperature rising was investigated by differential thermal analysis-thermogravimetry (DTA-TG). By combining the theoretical analysis with experimental results, the mechanism of oxygen releasing of copper ferrite is proposed, which is different from that of other ferrites. For copper ferrite, the oxygen releasing caused by Cu(II)→Cu(I) plays a predominant role, while for other ferrites, the oxygen releasing resulting from Fe(III)·Fe(II) is dominant. Supported by the National Defense Fundamental Research Fund (Grant No. A1420080145)