High catalytic activity of V2O5-ZrO2 modified with H2SO4 for propene partial oxidation

For V₂O₅–ZrO₂ catalysts, up to 10 mol% the crystalline structure of V₂O₅ was not observed, indicating a good dispersity the surface of ZrO₂. V₂O₅–ZrO₂ catalyst modified with H₂SO₄ exhibited much on higher catalytic activity for propene partial oxidation than unmodified catalysts due to the increased acidity and acid strength of modified catalyst.     

利用H2与金属氧化物的选择性反应从CO中除H2

研究了一些氧化物的H2－TPR及CO－TPR行为,结果发现,Co3O4／Al2O3,NiO／SiO2,NiO和Pd／NiO的H2－TPR温度要低于它们的CO－TPR温度,特别是Pd／NiO样品,它的H2－TPR温度为598K,而其CO－TPR温度高达949K,差别为351K,因此有可能利用Pd／NiO在一定温度下选择性地与CO中的H2反应而将其除去. 实验结果表明,Pd／NiO可在603K及4000h-1的条件下从H2（0.34％）,CO（50％）和N2（余）的混合气中选择性地除去90％以上的H2,吸氢容量为每克样品55mL标准态H2.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Synthesis, structure, and properties of [Re2(HPO4)2(H2PO4)2(H2O)2] · 4H2O

The complex [Re₂(HPO₄)₂(H₂PO₄)₂(H₂O)₂] · 4H₂O (I) was synthesized and investigated by conductometric, potentiometric, electronic and vibration spectroscopic methods. Thermal behavior of the title compound was studied and its molecular structure was determined from X-ray diffraction data. In the dimeric neutral complex, the bridging pairs of the hydrophosphate and dihydrophosphate groups close four five-membered Re-O-P-O-Re chelate rings. The O atom of water molecule occupies the axial position in the metal coordination polyhedron. The Re-Re distance 2.2168(8) ? corresponds to quadruple bond. Original Russian Text ? A.V. Shtemenko, V.G. Stolyarenko, K.V. Domasevich, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 2, pp. 83–88.     

Coordination Polymers of Scandium Sulfate. Crystal Structures of (H2Bipy)[Sc(H2O)(SO4)2]2 · 2H2O and (H2Bipy)[HSO4]2

Compounds with the general formula Cat_x[Sc(H₂O)_z(SO₄)_y] · nH₂O (Cat = NH₄, H₂Bipy (Bipy is 4,4′-bipyridine), and HEdp (Edp is ethylenedipyridine) are synthesized and identified by elemental analysis and IR spectral data. The X-ray diffraction analysis of (H₂Bipy)[Sc(H₂O)(SO₄)₂]₂ · 2H₂O shows that in the structure of this compound, the chains of ScO₆ octahedra and SO₄ tetrahedra are united to form ribbons due to the tridentate coordination of the sulfate ion. The ribbons form a framework, whose infinite cavities contain H₂Bipy²⁺ cations.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 576–582.Original Russian Text Copyright © 2005 by Petrosyants, Ilyukhin, Sukhorukov.     

Magnetic and catalytic properties of the 2D copper(II) functionalized VPO hybrid system [{Cu(bpy)}2(VO)3(PO4)2(HPO4)2]·2H2O

The hybrid 2D compound [{Cu(bpy)}₂(VO)₃(PO₄)₂(HPO₄)₂]·2H₂O (1), has been investigated due to its interesting magnetic and catalytic properties. Compound (1) acts as an efficient catalyst in the epoxidation of cyclohexene and styrene. The chemoselectivity towards the epoxidation of cyclohexene is notoriously higher than the one observed towards styrene. The bulk antiferromagnetic behaviour of [{Cu(bpy)}₂(VO)₃(PO₄)₂(HPO₄)₂]·2H₂O (1) can be well described with a pentanuclear model, using five J values. Both antiferromagnetic and ferromagnetic interactions mediated by phosphate bridges are found to be present in this hybrid copper(II)–vanadium(IV) material.     

Zersetzung von H2O2 durch den Resol-Xanthat-Cu(II)-Komplex

Ohne Zusammenfassung     

Structure of uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2(OOCC≡CCOO)2 · H2O] · 2H2O and Cs2[UO2(OOCC≡CCOO)2 · H2O] · 2H2O

Uranyl complexes with acetylenedicarboxylic acid, K(H₅O₂)[UO₂L₂H₂O] · 2H₂O (I) and Cs₂[UO₂L₂H₂O] · 2H₂O (II), L²⁻ = C₄O ₄ ²⁻ were prepared for the first time. The composition and structure of the complexes were determined by X-ray diffraction. The crystal data are as follows: a = 16.254(12) ?, b = 13.508(8) ?, c = 7.683(6) ?, β = 90.91(7)°, space group C2/c, V = 1687(2) ?³ (I); a = 7.0745(10), b = 18.4246(10), c = 13.1383(10) ?, space group Abm2, V = 1712.5(3) ?³ (II). The structures of I and II are based on [UO₂L₂H₂O] _n ²⁻ anionic chains stretched along the [101] direction (I) or [010] direction (II). In I and II, the uranium coordination polyhedron is a pentagonal bipyramid in which the equatorial environment of the uranyl ions is formed by the oxygen atoms of the four L²⁻ anions and the water molecule. The L²⁻ anions in I and II are bidentate bridging ligands connecting two uranium atoms that are next to each other in the anionic chain; their coordination capacity is equal to 2. In I, the K⁺ and H₅O ₂ ⁺ cations are outer-sphere species. The latter form hydrogen bonds combining the anionic chains shifted by translation b with respect to each other. The [UO₂L₂H₂O] _n ²⁻ chains in I are surrounded by the potassium and oxonium cations; in II, these are combined by hydrogen bonds into anionic layers between which Cs⁺ cations are arranged. The IR spectrum of compound II was measured and interpreted. Original Russian Text ? I.A. Charushnikova, A.M. Fedoseev, N.A. Budantseva, I.N. Polyakova, Ph. Moisy, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 63–69.     

三维超分子[Ni(hmt)2(SCN)2(H2O)2][Ni(SCN)2(H2O)4](H2O)2的自组装,晶体结构及磁性质(hmt=六次甲基四胺)

Compound [Ni(hmt)₂(SCN)₂(H₂O)₂][Ni(SCN)₂(H₂O)₄](H₂O)₂ (hmt=hexamethylenetetramine) was pre-pared and structurally characterized by means of X-ray single crystal diffraction. The two neutral units [Ni(hmt)₂(SCN)₂(H₂O)₂] and [Ni(SCN)₂(H₂O)₄] are joined together through hydrogen bonds N…H-O, O…H-O and S…H-O. In the solid state, the compound has three-dimensional network structure. The determination of its variable-temperature magnetic susceptibilities (5～300K) shows that the magnetic behavior obeys the Curie-Weiss law over the whole temperature ranges.     

Ferromagnetic exchange coupling in phosphonato-bridged dinuclear copper(II) compound with monoethyl (pyridyn-2-ylmethyl)phosphonate ligand (2-mpmpe): Cu2(2-mpmpe)2(H2O)2(NO3)2

The interaction of diethyl (pyridyn-2-ylmethyl)phosphonate (2-pmpe) with Cu(NO₃)₂ · 6H₂O leads to a partial hydrolysis of the starting ligand and formation of the compound of the formula Cu₂(2-mpmpe)₂(H₂O)₂(NO₃)₂, where 2-mpmpe = monoethyl (pyridyn-2-ylmethyl)phosphonate. The crystal and molecular structure of a copper(II) compound was determined by single X-ray diffraction method. Its structure consists of five-coordinated in distorted square planar geometry (CuNO₄ chromophore) copper(II) ions doubly bridged by OPO from phosphonate. The Cu?Cu distance is 4.69 Å. The crystal packing is determined by the interdinuclear hydrogen bond system, which leads to a three-dimensional (3D) H-bonds network. The compound was characterized by infrared, ligand field, EPR spectroscopy, and magnetic studies. The magnetic properties of the title compound investigated over the 1.8–300 K, revealed the occurrence of a weak ferromagnetic coupling through phosphonate bridge (J = 1.86 cm⁻¹) and interdimer superexchange coupling through H-bond network (zJ′ = −0.17 cm⁻¹). Spectroscopic and magnetic properties are presented in the light of crystal structure.     

Chemoselective hydrogenation of nitroarenes and deoxygenation of pyridine N-oxides with H2 catalyzed by MoO2Cl2

A chemoselective and highly efficient hydrogenation of nitroarenes and deoxygenation of pyridine N-oxides using a cheap and environmentally friendly H₂/MoO₂Cl₂ system has been developed     

Simulation of dielectric properties and stability of clusters (H2O)i, CO2(H2O)i, and CH4(H2O)i

Molecular dynamics method is used for studying complex permittivity ɛ and the stability of individual water clusters as a function of the number of involved molecules (7 ≤ i ≤ 20) and also the corresponding characteristics of water aggregates with a captured CO₂ or CH₄ molecule. Absorption of the latter molecules leads to considerable changes in dielectric properties and stability of clusters. In particular, upon the addition of a CO₂ molecule to a water cluster, the oscillation parameters of the real and imaginary parts of the permittivity change. Capture of a CH₄ molecule by a water aggregate changes the ɛ(ω) dependence from the relaxation to resonance type. For i ≥ 15, the thermal stability of individual water clusters can be lower than that of aggregates CO₂(H₂O) _i and CH₄(H₂O) _i . The mechanical stability of (H₂O) _{i ≥ 13} clusters can exceed that of heteroclusters under consideration. Clusters (H₂O) _i and CO₂(H₂O) _i have approximately the same dielectric stability, whereas aggregates CH₄(H₂O) _i exhibit lower stability with respect to electric perturbations. Original Russian Text ? A.E. Galashev, V.N. Chukanov, A.N. Novruzov, O.A. Novruzova, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 143–153.     

CO/H2 and CO2/H2 reactions with amorphous carbon-metal catalysts

By metal impregnation of selected naturally occurring organic materials followed by controlled carbonization, metal semicoke catalysts can be readily prepared. These catalysts have been tested in the synthesis of hydrocarbons and alcohols from CO/H₂ and CO₂/H₂ mixtures. Fe and Co preparations have been used. Relatively high temperatures are required when using these catalysts, which are quite active for synthesis using CO₂ and H₂. The pressure (5150 kPa) is very favorable both for the synthesis of liquid hydrocarbons (C₅–C₃₀) and alcohols (C₁–C₅).

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. CO/H₂ CO₂/H₂. Fe Co. , CO₂ H₂. 5150 ) (C₅–C₃₀) (C₁–C₅).

     

Selective epoxidation of monoterpenes with H2O2 and polymer-supported methylrheniumtrioxide systems

A convenient and efficient synthesis of monoterpene epoxides by application of heterogeneous poly(4-vinylpyridine)/methyl rhenium trioxide (PVP/MTO) and polystyrene/methyl rhenium trioxide (PS/MTO) systems is described. Even highly sensitive terpenic epoxides were obtained in excellent yield. Environment friendly, easily available, and low cost H₂O₂ was used as oxidant. Catalysts were stable systems for at least five recycling experiments.     

Epr studies on copper(II) [2,5-diphenyloxazole]2 (Clo4)2·4H2O

EPR studies have been carried out on the title complex in polycrystalline and solution forms at room and low temperatures. These studies in polycrystalline sample are indicative of oxygen coordination. In N,N'-dimethylformamide and pyridine solutions of this complex, the solvent molecules are found to occupy the coordination positions of copper(II).     

Jahn-Teller-distorted dimeric anions in (cat)[Mn2F8(H2O)2]·2H2O (cat = pipzH2, dabcoH2) and (dabcoH2)2[Mn2F8(H2PO4)2]

Using biprotonated dabco (1,4-diazabicyclo[2.2.2]octane) or pipz (piperazine) as counter cations, mixed-ligand fluoromanganates(III) with dimeric anions could be prepared from hydrofluoric acid solutions. The crystal structures were determined by X-ray diffraction on single crystals: dabcoH₂[Mn₂F₈(H₂O)₂]·2H₂O (1), space group P2₁, Z = 2, a = 6.944(1), b = 14.689(3), c = 7.307(1) Å, β = 93.75(3)°, R₁ = 0.0240; pipzH₂[Mn₂F₈(H₂O)₂]·2H₂O (2), space group , Z = 2, a = 6.977(1), b = 8.760(2), c = 12.584(3) Å, α = 83.79(3), β = 74.25(3), γ = 71.20(3)°, R₁ = 0.0451; (dabcoH₂)₂[Mn₂F₈(H₂PO₄)₂] (3), space group P2₁/n, Z = 4, a = 9.3447(4), b = 12.5208(4), c = 9.7591(6) Å, β = 94.392(8)°, R₁ = 0.0280. All three compounds show dimeric anions formed by [MnF₅O] octahedra (O from oxo ligands) sharing a common edge, with strongly asymmetric double fluorine bridges. In contrast to analogous dimeric anions of Al or Fe(III), the oxo ligands (H₂O (1,2) or phosphate (3)) are in equatorial trans-positions within the bridging plane. The strong pseudo-Jahn-Teller effect of octahedral Mn(III) complexes is documented in a huge elongation of an octahedral axis, namely that including the long bridging Mn-F bond and the Mn-O bond. In spite of different charge of the anion in the fluoride phosphate, the octahedral geometry is almost the same as in the aqua-fluoro compounds. The strong distortion is reflected also in the ligand field spectra.     

Selective catalytic oxidation of NO with O2 over Ce-doped MnOx/TiO2 catalysts

A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=1/3 and calcined at 300°C shows a superior activity for NO oxidation to NO2. On Ce(1)Mn(3)Ti catalyst, 58% NO conversion was obtained at 200°C and 85% NO conversion at 250°C with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst (48% at 250°C). Characterization results implied that the higher activity of Ce(1)Mn(3)Ti could be attributed to the enrichment of well-dispersed MnOx on the surface and the abundance of Mn3+ and Ti3+ species. The addition of Ce into MnOx/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.     

Synthesis,crystal structure and catalytic activity for H2O2 disproportionation of the manganese(II) coordination polymer {[Mn(O2C(CF2)8CO2)(phen)2]H2O}n (phen = 1,10-phenanthroline)

The title polymeric complex {[Mn(O₂C(CF₂)₈CO₂)(phen)₂]H₂O}_n was synthesized through the reaction of 1,10-phenanthroline, perfluorosebacic acid and MnCO₃ · H₂O. The molecular structure was characterized by X-ray diffraction, elemental analysis, thermal gravimetry, IR and UV–Vis spectroscopy and its catalytic activity has been studied. X-ray structure analysis shows that each Mn(II) ion is octahedrally coordinated by two bidentate phenanthroline ligands and the carboxylate oxygen atoms from two symmetry related perfluorosebacate ligands, which are coordinated in cisoid positions. The structure consists of polymeric chains, with the perfluorosebacato ligand bridging the Mn(II) ions in a monodentate fashion. Crystallographic characterization shows a supramolecular structure involving hydrogen bonds, π–π and π-ring interactions. The catalytic results indicated that the complex has reasonably good activity towards the disproportionation of hydrogen peroxide into water and dioxygen in methanol and it does not exhibit saturation kinetics with the substrate. The initial reaction rates and their temperature and base dependencies were investigated by monitoring the dioxygen evolution. Kinetic studies revealed a first-order dependence on the catalyst concentration. Activation parameters have been calculated at 301 K.     

Coordination of water to organolead(IV) nitrates: The examples of [PbPh2(NO3)2(H2O)2] and [PbMe3(NO3)(H2O)]

The compound [PbPh₂(NO₃)₂(H₂O)₂] was synthesized and characterized by spectroscopic methods (IR; ¹H, ¹³C and ²⁰⁷Pb NMR) and mass spectrometry. An X-ray diffraction study showed that the crystal is a supramolecular tridimensional network of hydrogen-bonded PbPh₂(NO₃)₂(H₂O)₂ units in which the Pb atom is octacoordinated and adopts a distorted hexagonal bipyramidal geometry, with four O (bidentate nitrate) and two O (water) atoms in equatorial positions and two C-phenyl atoms in axial positions. The crystal of [PbMe₃(NO₃)(H₂O)], obtained as a byproduct in the synthesis of PbMe₂(NO₃)₂, contains chains of hydrogen-bonded PbMe₃(NO₃)(H₂O) units in which the Pb atom is pentacoordinated with a slightly distorted trigonal bipyramidal environment. In this arrangement the three C-methyl atoms are equatorial and the O atoms from the monodentate nitrate and the water molecule are axial.     

Synthesis and structure of [Ce2(H2O)3](C2O4)2.5(H3C2O3) and Ce2(C2O4)(H3C2O3)4: The latter structure presents an interesting new framework, with 2-fold interpenetration

Single crystals of two cerium complexes, with mixed-ligands oxalate and glycolate, have been prepared in a closed system, at 200 °C for one month: [Ce₂(H₂O)₃](C₂O₄)_2.5(H₃C₂O₃) 1 and Ce₂(C₂O₄)(H₃C₂O₃)₄2. 1 crystallizes in the orthorhombic system, space group Pbca, with , , and while 2 crystallizes in the tetragonal system, space group P4₂/nbc, with , . For both complexes, the three-dimensional framework structure is built up by the linkages of the cerium and all the oxygen atoms of oxalate and glycolate ligands. For 2, its structure presents a nice case of two 3D identical sub-lattices, with 2-fold interpenetration. The only link between these two sub-lattices is assumed by strong hydrogen bonds between the hydroxyl function of the glycolate and the oxygen atoms of the oxalate. The schematized framework of 2, including only the cerium atoms, can be compared to that of cooperite (PtS).For 1, the two independent cerium have 9- or 10-fold coordination, forming a distorted monocapped or bicapped square antiprism polyhedron while for 2, the two independent cerium present 8-fold coordination, forming an almost regular dodecahedron. A quite relevant feature of 2 is the complete absence of water. 2 has been extended to other lanthanides (Ln=Ce…Lu, yttrium included) leading to a family, which has been characterized by infra-red and thermal analysis.