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1.
The novel branched chain-type nitridosilicates Ce5Si3N9 and La5Si3N9 have been synthesized in a radio-frequency furnace starting from the respective metals and silicon diimide Si(NH)2 at 1625 °C for La5Si3N9 and 1650 °C for Ce5Si3N9, respectively. The structure of Ce5Si3N9 has been determined by single-crystal X-ray diffraction (Ce5Si3N9, Cmca (no. 64), a = 10.567(2) Å, b = 11.329(2) Å, c = 15.865(3) Å, V = 1899.3 Å3, Z = 8, R1 = 0.0391, 1480 independent reflections, 90 refined parameters). The structure of isotypic La5Si3N9 has been refined by the Rietveld method, starting from single-crystal data of Ce5Si3N9 (La5Si3N9, Cmca (no. 64), a = 10.647(4) Å, b = 11.414(4) Å, c = 16.030(5) Å, V = 1948.1 Å3, Z = 8, RP = 0.0348, RF2 = 0.0533). Both compounds are built up of alternating Q2- and Q3-type corner sharing SiN4 tetrahedra with additional corner sharing Q1-units attached to the Q3-tetrahedra pointing alternately in opposing directions. These zipper-like chains are intertwined in both directions perpendicular to the chain itself to form a three-dimensionally interlocked structure with the rare-earth ions situated between the chains. Magnetic measurements resulted in a ferromagnetic ground state with a magnetic moment in agreement with Ce3+.  相似文献   

2.
Aggregation of several chemicals from biomass: furfural derived compounds (furfural, 5-methylfurfural, furfuryl alcohol and tetrahydrofurfuryl alcohol), lactate derived compounds (methyl lactate, ethyl lactate and butyl lactate), acrylate derived compound (methyl acrylate) and levulinate compounds (methyl levulinate, ethyl levulinate and butyl levulinate) in aqueous solution has been characterised at T = 298.15 K through density, ρ, speed of sound, u, and isentropic compressibilities, κS, measurements. In addition the standard Gibbs free energies of aggregation have been also calculated. Furthermore, in order to deepen insight the behaviour of these chemicals in aqueous solution, the solubility of these compounds has been measured at T = 298.15 K.  相似文献   

3.
《Chemical physics》2005,308(1-2):147-157
Quantum rotations of NH3 groups in Hofmann clathrates Ni–Ni–C6H6 and Ni–Ni–C12H10 have been studied using inelastic neutron scattering. Calculations of the dynamical structure factor for a free uniaxial quantum rotor reproduce the neutron scattering data with respect to their Q- and T-dependence as well as the relative intensities for the 0  1, 0  2 and 1  2 transitions. Though the effective NH3 rotation constant is different from the gas phase value, the effective radius of rotation (i.e., the average distance of protons from the rotation axis) is equal or very close to the geometrical value r = 0.94 Å for a NH3 group. Comparing the experimental data with the calculated dynamical structure factor for the 0  3 transition it could be shown, that the corresponding transition line, in contrast to transitions between j = 0,1,2 levels measured so far, has a finite width at T = 0 K.  相似文献   

4.
The synthesis of new ruthenium-based catalysts applicable for both homogeneous and heterogeneous metathesis is described. Starting from the Hoveyda-Grubbs first generation (1) and the Hoveyda-Grubbs second generation (2) catalysts the homogeneous catalysts [RuCl((RO)3Si–C3H6–N(R′)–CO–C3F6–COO)(CH–o-O–iPr–C6H4)(SIMes)] (4: R = Et, R′ = H; 5: R = R′ = Me) (SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) were prepared by substitution of one chloride ligand with trialkoxysilyl functionalized silver carboxylates (RO)3Si–C3H6–N(R′)–CO–C3F6–COOAg (3a: R = Et, R′ = H; 3b: R = R′ = Me). These homogeneous ruthenium-species are among a few known examples with mixed anionic ligands. Exchange of both chloride ligands afforded the catalysts [Ru((RO)3Si–C3H6–N(R′)–CO–C3F6–COO)(CH–o-O–iPr–C6H4)(SIMes)] (9: R = Et, R′ = H; 11: R = R′ = Me) and [Ru((RO)3Si–C3H6–N(R′)–CO–C3F6–COO)(CH–o-O–iPr–C6H4)(PCy3)] (8: R = Et, R′ = H; 10: R = R′ = Me). The reactivity of the new complexes was tested in homogeneous ring-closing metathesis (RCM) of N,N-diallyl-p-toluenesulfonamide and TONs of up to 5000 were achieved. Heterogeneous catalysts were obtained by reaction of 4, 5 and 811 with silica gel (SG-60). The resultant supported catalysts 4a, 5a, 8a11a showed reduced activity compared to their homogenous analogues, but rival the activity of similar heterogeneous systems.  相似文献   

5.
Using the polyfunctional ligand 2-phosphonethanesulfonic acid (H3L) a high-throughput (HT) study was started for the systematic investigation of the system SrCl2/H3L/NaOH/H2O. The HT experiment comprising 48 individual reactions were performed to systematically investigate the influence of pH of the starting mixture as well as the molar ratio Sr2+:H3L. Two new compounds SrH(O3P–C2H4–SO3) (1) and Sr3(O3P–C2H4–SO3)2(H2O)2 (2) were obtained and structurally characterized by single-crystal X-ray diffraction. The reaction products synthesized under hydrothermal conditions always contain traces of SrSO4, which are due to the decomposition of small amounts of the ligand. While compound 2 could only be obtained under hydrothermal conditions, the synthesis of 1 could be accomplished under milder reaction conditions and a reaction scale-up could be performed. Compound 1 crystallizes in a monoclinic system with space group C2/c (no. 15), a = 534.73(11) pm, b = 1648.7(3) pm, c = 825.43(17) pm, β = 105.34(3)°, V = 701.8(2)–106 pm3, Z = 4, R1 = 0.0268, and wR2 = 0.0642 for I > 2σ(I). Compound 2 crystallizes in a triclinic system with space group P-1 (no. 2), a = 700.97(14) pm, b = 1008.5(2) pm, c = 1274.8(3) pm, α = 97.63(3)°, β = 92.03(3)°, γ = 92.03(3)°, V = 843.7(3)–106 pm3, Z = 2, R1 = 0.0360, and wR2 = 0.0896 for I > 2σ(I). In the structure of compound 1 the phosphorous and sulfur atoms cannot be distinguished due to identical crystallographic positions. Thus, an averaged structure was obtained which is built up by edge-sharing SrO8 polyhedra that form infinite M–O–M chains. Compound 2 contains corner-, edge-, and face-sharing SrO8 polyhedra which form inorganic M–O–M layers. These M–O–M chains (1) and layers (2) are connected to a three-dimensional network by the –CH2CH2– group of the ligand, respectively. Additional characterization by thermogravimetric analysis and IR-spectroscopy for compound 1 is also presented.  相似文献   

6.
The temperature dependence of the rate constant of the inversion substitution reactions CH3X + O2 → CH3O2? + X? (X = SH, NO2), can be expressed as k = 6.8 × 10–12(T/1000)1.49exp(–62816 cal mol–1/RT) cm3 s–1 (X = SH) and k = 6.8 × 10–12(T/1000)1.26 × × exp(–61319 cal mol–1/RT) cm3 s–1 (X = NO2), as found with the use of high-level quantum chemical methods and the transition state theory.  相似文献   

7.
《Comptes Rendus Chimie》2015,18(12):1264-1269
A one-step CO2 hydrogenation reaction into hydrocarbons (HC) using a bifunctional system constituted by a methanol synthesis catalyst [Cu–ZnO–Al2O3 (CZA)] and a zeolite (HZSM-5) has been studied. The influence of the catalyst bed configuration on activity, selectivity, and HC yield has been evaluated. The results obtained at TR = 623 K, PR = 3.0 MPa and WHSV = 6000 h−1 show that CO2 hydrogenation and hydrocarbon selectivity were strongly influenced by the proximity between oxide and zeolite, whatever the disposition of the two catalytic active sites. Indeed, the highest conversion and the best yield of hydrocarbons (mainly C2) were obtained with the M1 bifunctional catalysts in which the oxide–zeolite proximity is the lowest. This is ascribed to the hydrogen spillover phenomenon, which does not promote the carbon chain growth.  相似文献   

8.
The H–D exchange processes in MHn or MDn hydrides (M = As, Sb, Bi, n = 3; M = Ge, Sn, n = 4) taking place when they are in contact with H2O or D2O solution at different pH or pD values (interval of pH = [0,13]) have been investigated using gas chromatography–mass spectrometry (GC-MS). MHn or MDn compounds were injected into the headspace of reaction vials (4–12 ml) containing 1–2 ml of buffered solution maintained under stirring or shaking conditions. The isotopic composition of the gaseous phase hydrides/deuterides was determined at regular intervals in the range of time 0–15 min. The MHn or MDn compounds were synthesized in separate vials and their purity was checked separately before injection into the reaction vials. The mass spectra were deconvoluted in order to estimate the relative abundance of each species formed following the H–D exchange process (AsHnD3−n , SbHnD3−n, BiHnD3−n, n = 0–3; GeHnD4−n, SnHnD4−n, n = 0–4) and the relative abundance of H and D. In the investigated pH (or pD) interval arsanes and stibanes undergo H–D exchange in alkaline media for pH > 7. No H–D exchange was detected for the other hydrides, where the prevailing process is their decomposition in the aqueous phase. A reaction model, based on the formation of protonated or deprotonated intermediates is proposed for H–D exchange of MHn or MDn compounds placed in contact with H2O or D2O at different pH or pD values. The H–D exchange in the already formed hydrides can be source of the interference in mechanistic studies on hydride formation performed using labeled reagents; no H–D exchange was detected within the following pH intervals that can be considered free from interference: arsanes pH = [0,7), stibanes pH = [0,7), bismuthanes, germanes and stannanes pH = [0,13].  相似文献   

9.
Alkyl and arylplatinum complexes with 1,5-cyclooctadiene ligand, [PtR2(cod)] (R = Me, Ph, C6H4-p-CF3, C6F5), react with secondary phosphines, PHR′2 (R′ = i-Bu, t-Bu, Ph), to afford the mononuclear platinum complexes, cis-[PtR2(PHR′2)2] (1a: R = Me, R′ = i-Bu; 1b: R = Me, R′ = t-Bu; 1c: R = Me, R′ = Ph; 2a: R = Ph, R′ = i-Bu; 2b: R = Ph, R′ = t-Bu; 2c: R = R′ = Ph; 3a: R = C6H4-p-CF3, R′ = i-Bu; 3b: R = C6H4-p-CF3, R′ = t-Bu; 3c: R = C6H4-p-CF3, R′ = Ph; 4a: R = C6F5, R′ = i-Bu; 4c: R = C6F5, R′ = Ph) in 81–98% yields. Molecular structures of the complexes except for 1a, 1c and 2a were determined by X-ray crystallography. Complex 1b has a square-planar structure with Pt–C(methyl) bonds of 2.083(8) and 2.109(8) Å, while the Pt–C(aryl) bonds of 2bc, 3ac, 4a and 4c (2.055(1)–2.073(8) Å) are shorter than them. Thermal decomposition of 1b, 2ac, and 3ac releases methane, biphenyl or 4,4′-bis(trifluoromethyl)biphenyl as the organic products, which are characterized by NMR spectroscopy. The solid product of the thermal reactions of 2b and 2c were characterized as the metallopolymers formulated as [Pt(PR′2)2]n (5b: R′ = tBu; 5c: R′ = Ph), based on the solid-state NMR and elemental analyses.  相似文献   

10.
《Solid State Sciences》2007,9(7):555-563
We report the single crystal structures and magnetic properties of a series of lanthanide-containing iridates, Ln1−xNa1+xIrO4 (Ln = Gd–Er, Y; x = 0.04–0.26) grown from a mixed sodium and cesium hydroxide flux. The compounds crystallize in the hexagonal space group P-62m (#189) with lattice parameters ranging from a = 9.3872(2)–9.4596(3) Å and c = 3.1512(1)–3.2030(2) Å and are structurally related to other iridium oxides. The oxidation state of iridium ranges from +4.08 (Gd) to +4.50 (Er). Magnetic susceptibility measurements reveal the existence of antiferromagnetic correlations below 15 K.  相似文献   

11.
12.
Reactions of Be2+ and Mg2+ with O2– in molten eutectic mixture (CsCs + KCl + NaCl) (0.455:0.245:0.30) at T = 783 K were studied by a potentiometric method using Pt(O2)|ZrO2(Y2O3) indicator electrode. Addition of O2– ions to the melt containing Mg2+ results in precipitation of MgO (pKs,MgO = 11.89 ± 0.3, molality) whereas interaction of Be2+ with O2– is accompanied with sequential formation of Be2O2+ (pK = 15.68 ± 0.5, molality) and precipitation of BeO (pKs,BeO = 9.62 ± 0.3, molality). On the basis of the obtained and known data pKs,MgOT−1 dependence in molten (CsCs + KCl + NaCl) eutectic is constructed. The slope of the said dependence in T/K = (from 583 to 1073) range is in good agreement with the value predicted by the Shreder equation, that extends the range of use of the Shreder equation for predictions of metal oxide solubilities in molten halides.  相似文献   

13.
《Solid State Sciences》2007,9(7):600-603
The utility of the concept of optical channel in understanding the optical properties of insulating materials was briefly reviewed by considering how the indices of refraction n of the seven TiO2 allotropes, TiOF2, TiF4 and the binary compounds MQ (M = Zn, Cd; Q = O, S, Se, Te) are related to their total absorption power per formula unit I(ɛ2) × V and their formula unit volume V. Important factors governing the optical properties of insulating materials are discussed.  相似文献   

14.
《Solid State Sciences》2007,9(6):455-458
The calcium trimellitate, Ca(H2O)[(O2C)2–C6H3–CO2H], was hydrothermally synthesized from a mixture of calcium hydroxide, 1,2,4-benzenetricarboxylic (or trimellitic) acid and water at 180 °C for 24 h (under autogenous pressure). Its crystal structure has been determined by single-crystal X-ray diffraction analysis using synchrotron radiation (station 9.8, SRS Daresbury, UK). It consists of infinite chains of calcium bicapped trigonal prismatic polyhedra connected to each other through the 1,2,4-benzenetricarboxylate ligand. The eight-fold coordinated calcium cation is bonded to one terminal water molecule, two carboxylate groups with a chelating conformation and three carboxylate groups in a monodentating mode. One of the monodentate carboxylate is terminal with the occurrence of protonated C–OH bonding.Triclinic space group P-1 with a = 6.9073(4) Å, b = 6.9917(4) Å, c = 10.3561(6) Å, α = 87.178(1)°, β = 83.233(1)°, γ = 69.576(1)°, V = 465.41(5) Å3.  相似文献   

15.
A new complex of oxovanadium(IV), V2O2[(HB(pz)3)2(pyrro)2 (1) and a dimer-dithio carboxyl compound (C5H8NS2)2 (2) have been synthesized by the reaction of VOSO4·nH2O with NaHB(pz)3 and pyrrolidine dithio carboxylic acid ammonium salt. They were characterized by element analysis, IR spectra, UV–vis spectra and X-ray diffraction. Structural analyses of 1 and 2 gave the following parameters: 1, triclinic, P-1, a = 7.732(4) Å, b = 14.285(8) Å, c = 17.802(9) Å, α = 101.314(8)°, β = 92.682(9)°, γ = 92.228(9)°, V = 1923.6(18) Å3, and Z = 4; 2, monoclinic, C2/c, a = 13.857(2) Å, b = 10.4213(18) Å, c = 9.436(2) Å, β = 97.099(2), V = 1352.1(4) Å3, and Z = 4. In complex 1, vanadium atom adopts a distorted tetragonal bipyramid structure, which is typical for oxovanadium(IV) complexes. Compound 2 is a dimer-dithio carboxyl compound with S–S bond. In addition, thermal analysis was performed for analyzing the stabilization of the complexes.  相似文献   

16.
The UV–vis spectra of recently synthesized 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-one, (I), and 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-thione, (II) were studied in aqueous methanol (5%, v/v methanol). The nature of the electronic transitions and the roles of carbonyl oxygen of I and thiocarbonyl sulfur of II on the behavior of UV–vis spectra were discussed.Acid–base equilibria of the compounds against varying pH and pKa values related equilibria were determined at an ionic strength of 0.10 M by using the Henderson–Haselbalch equation. The mean acidity constants for the protonated forms of the compounds were determined as pKa1 = 5.121, pKa2 = 7.929 and pKa3 = 11.130 for I and pKa1 = 4.684, pKa2 = 7.245 and pKa3 = 10.630 for II. The preferred dissociation mechanisms were discussed based on UV–vis data and a mechanism was proposed for each compound.  相似文献   

17.
Two new hybrid materials, (C4H14N2)[MII(H2O)6](SO4)2·4H2O (MII: Co (I), Ni (II)), have been synthesised by slow evaporation method at room temperature and crystallographically characterized. They crystallise isotypically in the monoclinic system, space group P21/n, with the following unit-cell parameters a = 9.2285(3), b = 11.3333(4), c = 10.6693(4) Å, β = 109.004(2)°, Z = 2 and V = 1055.07(6) Å3 for I and a = 9.2127(2), b = 11.3182(2), c = 10.6434(2) Å, β = 109.094(1)°, Z = 2 and V = 1048.74(4) Å3 for II. The structure of the two supramolecular compounds consists of metallic cation octahedrally coordinated to six water molecules, sulfate anions, 1,4-butanediammonium cation and water molecules linked together via two types of hydrogen bonds, O–H?O and N–H?O. The two compounds are not stable at room temperature and their partial dehydration depends on the humidity of the environment. The thermal decomposition of precursors, studied by thermogravimetric analysis (TG) and temperature-dependent X-ray diffraction (TDXD), shows successive intermediate hydrates and crystalline anhydrous compounds upon dehydration.  相似文献   

18.
Computational methods are used to investigate catalytic hydrophenylation of ethylene using complexes of the type [(Y)M(L)(CH3)(NCMe)]n+ [Y = Mp, n = 1; Y = Tp, n = 0; M = Ru or Os; L = PMe3, PF3, or CO; Mp = tris(pyrazolyl)methane; Tp = hydrido-tris(pyrazolyl)borate]. The conversion of ethylene and benzene to ethylbenzene with [(Y)M(L)(Ph)]n+ as catalyst involves four steps: (1) ethylene coordination, (2) ethylene insertion into the M–Ph bond, (3) benzene coordination, and (4) benzene C–H activation. DFT calculations form the basis to compare stoichiometric benzene C–H activation by [(Y)M(L)(CH3)(NCMe)]n+ complexes to yield methane and [(Y)M(L)(Ph)(NCMe)]n+. In addition, starting from the 16-electron species [(Y)M(L)(Ph)]n+, potential energy surfaces for the formation of ethylbenzene are calculated to reveal the impact of modifications to the scorpionate ligand (Mp or Tp), co-ligand (L) and metal center (M).  相似文献   

19.
The isothermal (vapour + liquid) equilibrium (VLE) (PTxiyi) was determined the binary systems of (ethyl acetate + diethyl carbonate) from T = (373.2 to 453.2) K, (ethyl acetate + phenyl acetate) at T = 373.2 K, and (diethyl carbonate + phenyl acetate) at T = 373.2 K, while the VLE (PTxi) of three diphenyl carbonate-containing binary systems was also determined experimentally at temperatures from (373.2 to 453.2) K. The experimental results show no azeotrope formation and near ideal solution behaviour for each binary system. These new VLE (PTxiyi) data have been passed by the point, area, and infinite dilution thermodynamic consistency tests. The Wilson-HOC, the NRTL-HOC, and the UNIQUAC-HOC models were applied to correlate the VLE results and the optimal values of the model parameters have been determined through data reduction. Comparable results were obtained from these three models.  相似文献   

20.
《Polyhedron》2005,24(16-17):2165-2172
Five new hydrogen-bonded solvated iron(II) complexes of pyrazolyl- and imidazolyl-based N,N-chelating ligands have been synthesised. Water to ligand-NH hydrogen-bonded bridges occur in the pseudo-dimeric complexes {cis-[Fe(pypzH)2(NCX)2]2(μ-OH2)(H2O)2} · H2O · MeOH (where X = S or Se), and in the chain complex {cis-[Fe(pypzH)2(NCS)2](μ-OH2)}n. A “half” spin-crossover (Tc = 125 K) was observed in the dimeric X = Se complex by means of magnetic measurements and no thermal hysteresis occurred between 4 and 300 K. The crystal structure at 123 K showed Fe–N distances consistent with the magnetism. Each Fe in the dimeric unit was structurally equivalent in the HS–LS state. Removal of the solvate molecules led to HS–HS behaviour over the temperature range 4–300 K. The pseudo-dimer with X = S also showed HS–HS behaviour as did the monomeric analogue cis-[Fe(pypzH)2(NCS)2]H2O and a structurally different methanol-bridged dimer {cis-[Fe(pyimH)2(NCS)2]2(μ-MeOH)2} · 2MeOH (pypzH = 2-(1H-pyrazol-3-yl)-pyridine; pyimH = 2-(1H-imidazol-2-yl)-pyridine).  相似文献   

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