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1.
Isothermal gravimetry and magnetic susceptibility of MoO3, MoAl2O3, CoAl2O3 and CoMoAl2O3 with/without Na+ ions have been studied in order to investigate the reducibility of the systems in H2 H2—hydrocarbons and H2—hydro-carbon—thiophene. These studies have evidenced the formation of metallic cobalt during reduction of cobalt—moly catalysts containing Na+ ions in the Al2O3 support. This metallic cobalt accelerates the reduction of supported MoO3. However, in the absence of sodium, cobalt exerts an inhibitory influence on the reduction of MoAl2O3. The inhibition is caused mainly due to retention of the water evolved during the process by well-dispersed Co2+ ions which are incapable of undergoing reduction. The presence of sulfur also kelps in suppressing the reduction to cobalt metal. 相似文献
2.
The crystal structures of SiPb2S4 and SiPb2Se4 were determined from three dimensional X-ray diffraction data collected with Mo radiation. Both structures are monoclinic with space group and 4 formula units per unit cell. Lattice dimensions for SiPb2S4 are a = 6.4721(5) Å, b = 6.6344(9) Å, c = 16.832(1) Å, and β = 108.805(7)°. For SiPb2Se4, a = 8.5670(2) Å, b = 7.0745(3) Å, c = 13.6160(3) Å, and β = 108.355(3)°. The Si is tetrahedrally coordinated to S and Se with SiS about 2.10 Å and SiSe about 2.27 Å. The structural framework can be described as consisting of trigonal prisms of S or Se atoms which form a prismatic tube by sharing the triangular faces. These tubes in turn share edges to form corrugated sheets, with the unshared edges projecting alternately on each side of the sheet. The structures are very similar but not identical. In the sulfide one Pb is in sevenfold coordination and the other crystallographically independent Pb is in eightfold coordination. The PbS distances range from 2.82–3.50 Å. In SiPb2Se4 both Pb atoms are in sevenfold coordination. PbSe distances range from 2.97 to 3.54 Å. In the sulfide the Pb atoms form a zig-zag chain within the channels formed by the prismatic tubes while in the selenide they are in a straight line. 相似文献
3.
Elucidation of the hydrodesulfurization (HDS) mechanism on molybdenum‐based catalysts using radioisotope tracer methods and reaction kinetics is reviewed. Firstly, to investigate the sulfidation state in Mo/Al2O3 and Co–Mo/Al2O3 catalysts, presulfiding of these catalysts has been performed using a 35S pulse tracer method. Secondly, HDS of radioactive 35S‐labeled dibenzothiophene was carried out over a series of sulfided molybdena–alumina catalysts and cobalt‐promoted molybdena–alumina catalysts in a pressurized flow reactor to estimate the behavior of sulfur on the working catalysts. Finally, sulfur exchange of a 35S‐labeled catalyst with hydrogen sulfide was performed to estimate the relationship between the amount of labile sulfur and catalytically active sites. 相似文献
4.
The IR spectra of paramagnetic Mo/V/ oxygen compounds that are claimed in the literature to be unstable, were measurement in the 4000–3000 and 1200–250 cm?1 regions. The spectra are poor but show a few bands in the valence and in the OH groups vibrations regions. Mo/V/ hydroxide can be reversibly or irreversibly dehydroxylated thermally in vacuum. The irreversible dehydroxylation of amorphous species containing Mo/V/ hydroxide takes place at >350°C, and is connected with a rearrengement of the atomic OMoO linkage and with crystallization of MoO3, MoO2 and Mo4O11 phases. 相似文献
5.
The electronegative ligand OTeF5 has been tested on the elements Ti, Mo, W, Ta, Re, Os and others. Compounds such as OMo(OTeF5)4, W(OTeF5)6, Ta(OTeF5)5, ReO2(OTeF5)3, OsO(OTeF5)4 are prepared. While ReVII could be stabilized with OTeF5, the highest oxidation state on Osmium is VI, and Iridium probably IV. OMo(OTeF5)4 shows a regular square pyramidal structure with apical double bonded oxygen. Chemistry on the ligand NTeF5 is based on the synthesis of H2NTeF5 and R3SiNHTeF51. Other new main group derivatives are so far Cl2NTeF5, HClNTeF5, OCN-TeF5, F3PNTeF5, Cl3NPTeF5, F2SNTeF5 and Cl2SeNTeF5, the first compound with a selenium-nitrogen double bond. In the transition metal series the compounds F4MoNTeF5 and Cl4WNTeF5 (in addition to the longer known polymeric (HgNTeF51) have been prepared. Both have discrete metal nitrogen double bonds. 相似文献
6.
《Coordination chemistry reviews》2001,213(1):51-77
This article summarizes and presents the obtainable characteristic IR spectra of the existing heterothiometallic cluster compounds containing the [MXS3]2− (X=O, S; M=V, Mo, W, Re) moiety. The MS stretching vibration modes are classified into four categories including ν(MSt), ν(Mμ2-S), ν(Mμ3-S) and ν(Mμ4-S) according to the different conjunction ways between the transition metal and sulfur atoms. The structures of the heterothiometallic cluster compounds could be inferred from their characteristic IR spectra, the core structure's symmetry of the heterothiometallic clusters and the M/M′ ratio. 相似文献
7.
B.M. Landsberg 《Chemical physics letters》1979,60(2):265-270
A new molecular species has been detected by passing HBr gas through dry AgNCSe, which is shown by consideration of the rotational constants of the four isotopic species H14N12C80Se, H14N12C78Se, H14N13C80Se and D14N12C80Se to be HNCSe. The spectrum is consistent with that of a quasilinear molecule. A preliminary structure has been determined having r(HN) = 0.99 A, r(NC) = 1.95 A, r(CSe) = 1.717 A and a mean HNC angle of 143°. The quadrupole interaction parameter eQq = 1.17 MHz and the dipole moment component μa = 1.98 D have also been determined. 相似文献
8.
《Polyhedron》1987,6(7):1551-1557
In ethereal solutions, WSCl4 and 4 equiv LiOR (R = But or Pri) react to form compounds of formula W(S)(OR)4. A single-crystal X-ray diffraction study of W(S)(O-But)4 showed it to have a square-based pyramidal geometry with an apical sulfide ligand. Pertinent bond distances (Å) and angles (°) are: WS = 2.1396(13), WO(av.) = 1.886(3), SWO(av.) = 105.09(10), WOC(av.) = 143.47(27). The tert-butoxide compound is stable toward sulfur atom abstraction by phosphines, and neither compound has shown any tendency to undergo comproportionations with W2(OR)6 (R = Pri or CH2But) species to form compounds of formula W3(μ3-S)(OR)10, in direct contrast to analogous molybdenum and tungsten oxo alkoxides. 相似文献
9.
John D. Corbett 《Journal of solid state chemistry》1981,39(1):56-74
A useful measure of the total MoMo bonding in diverse phases containing Mo6Y8-type clusters (Y = S, Se, Cl, Br) is given by the Pauling bond order sum per electron (). These fall into two classes: (a) strongly bonded examples with values near 1.00 which contain either discrete clusters with extra outer (exo) atoms or infinite confacial clusters, and (b) the rhombohedral Mo6Ch8 and MxMo6Ch8 Chevrel phases with reduced values of 0.72–0.84 in which face-capping chalcogenide (Ch) must also fill exo positions. The matrix effect in the latter which is responsible for the reduced bond orders arises from a combination of particularly strong MoCh intercluster bonds and closed-shell ChCh repulsions [3.31 å (S), 3.38 å (Se)], which force an elongation of the Mo6 trigonal antiprism and reduce the MoMo bonding. There is no distinction between sulfide and selenide Chevrel phases in the degree of total MoMo bonding as expressed in bond orders. Changes in the structure on reduction are analyzed; the major effects come from loosening of the intercluster MoCh bonding and thence a decreased distortion (matrix effect) together with a flexing of the Mo6Ch8 host according to the size and charge of M. Distance considerations indicate substantial covalency between some M and Ch2, especially Pb and Ag, while cell volumes and MoCh2 distances suggest significant constriction occurs in phases with higher charged M, possibly owing to compression by the host lattice and coulombic contributions to binding. Evidence for MoM bonding with M = Fe, Co, Ni is also noted. Intercluster interactions and MoMo bonding in Mo6S6Br2 and in the mixed Mo6Ch8MonChm (n = 9,12) cluster phases are quite consistent with those in the Chevrel phases, the total MoMo bonding per electron increasing with cluster condensation owing principally to reduce ChCh repulsions. 相似文献
10.
Grörgy Bor Giovanni Battiston Gino Sbrignadello 《Journal of organometallic chemistry》1976,122(3):413-418
The high-energy factored model (“CottonKraihanzel type”, non-rigorous force field) is capable of reproducing within ± 0.8 cm?1 all the CO and NO stretching frequencies of six different isotopic species of Co(CO)3NO, if the model is modified by the introduction of “effective atomic masses” which take into account that, in line with Miller's approach, the quantities dealt with refer to the composite properties of the MCO (or MNO) units. The results obtained by the same method for the isotopically substituted species of Ni(CO)4, Fe(CO)5, and M(CO)6 [M Cr, Mo, or W] are also in good agreement with experiment. 相似文献
11.
I. Galaţeanu V. V. Lungu D. Viorel 《Journal of Radioanalytical and Nuclear Chemistry》1976,33(2):273-285
The radiation stability of methionine-35S and selenomethionine75Se was investigated using the methods of thin-layer chromatography, gas chromatography and ESR. Radiation decomposition of
methionine-35S mainly consists in an oxidation process and in the release of volatile products. The ESR-spectra of irradiated DL-methionine
indicated a strong localization of the unpaired electrons on sulfur atoms. Radiation damage to selenomethionine-75Se as a function of radiation dose proved an increased stability of this compound, and its radiation decomposition consists
in the formation of oxidized products and by direct rupture of the selenium bonds accompanied by the formation of volatile
compounds like CH3SeH and SeH2. The self-radiolysis of the aqueous solution of selenomethionine-75Se during its storage in air leads, however, to a lower decomposition rate which consists in the release of inorganic selenium
and in an oxidation process. 相似文献
12.
Atilla Karaar Matthias Freytag Holger Thnnessen Jan Omelanczuk Peter G. Jones Rainer Bartsch Reinhard Schmutzler 《无机化学与普通化学杂志》2000,626(11):2361-2372
Treatment of 1,8‐bis(diphenylphosphino)naphthalene (dppn, 1 ) with stoichiometric amounts of sulfur or selenium in toluene at 80 °C selectively afforded the diphosphine monochalcogenides 1‐Ph2P(C10H6)‐8‐P(:S)Ph2 (dppnS, 2 a ) and 1‐Ph2P(C10H6)‐8‐P(:Se)Ph2 (dppnSe, 2 b ). The 31P{1H} NMR spectrum of 2 b showed an unusually large 5J(P–Se) value, which indicates a significant through‐space coupling component. The monosulfide acted as a bidentate P,S‐ligand towards platinum(II) ( 3 a ), whereas the corresponding monoselenide complex ( 3 b ′) lost elemental selenium with formation of the previously reported complex [PtCl2(dppn)‐P,P′] ( 3 ). Treatment of dppnSe with [(nor)Mo(CO)4] (nor = norbornadiene) led to formation of [(dppnSe)Mo(CO)4‐P,Se] ( 3 b ). Solutions of the latter slowly deposited Se with formation of [(dppn)Mo(CO)4‐P,P′] ( 4 ) which was also obtained by independent synthesis from 1 and [(nor)Mo(CO)4]. All isolated new compounds were characterised by a combination of 31P, 1H, 13C and 77Se ( 2 b ) NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. Single‐crystal X‐ray structure determinations were performed for dppnSe ( 2 b ), [PtCl2(dppnS)‐P,S] ( 3 a ), [(dppnSe)Mo(CO)4‐P,Se] ( 3 b ) and [(dppn)Mo(CO)4‐P,P′] ( 4 ). In 2 b steric effects cause the naphthalene ring to be distorted and force the phosphorus atoms by 65 and 59 pm to opposite sides of the best naphthalene plane. In the metal complexes 3 a , 3 b and 4 the phosphino‐phosphinochalcogenyl systems act as bidentate ligands through the P and the chalcogen atoms. The naphthalene systems are again distorted. The two independent molecules of 4 differ in their conformations. 相似文献
13.
《Journal of organometallic chemistry》1987,321(3):339-352
By means of the addition of the PH-functional methylenebisphosphanes R1R2-PCH2PR3H (PCP) to the MoMo triple bond in (η5-C5H5)2Mo2(CO)4(MoMo) the complexes (η5-C5H5)2Mo2(CO)4(PCP) containing a five-membered ring system Mo2P2C are obtained. Starting with unsymmetrically substituted methylenebisphosphanes R′2PCH2PRH only one isomer is formed, while the disecondary derivatives RHPCH2PHR (as the diastereomeric mixture) gave two isomers of (η5-C5H5)2Mo2(CO)4(PCP) (A2 and AB) as indicated by the 31P{1H} and 13C{1H} NMR spectra.X-ray structural analysis of the derivative of the racemate of t-BuHPCH2PH(t-Bu) space group C2/c, monoclinic, a 18.034(2), b 14.909(1), c 11.106(1) Å, α 90, β 99.788(8), γ 90°) reveals a puckered Mo2P2C five-membered ring system (dihedral angle PMoMo′P′ 54.4(2)°) with square-pyramidal coordination geometry at the Mo atoms. Two of the CO ligands (C(6)O(1) and C(6′)O(1′)) are almost coplanar with the molybdenum atoms, while the terminal CO groups (C(7)O(2) and C(7′)O(2′)) are about orthogonal (dihedral angle C(7)MoMo′C(7′) 88.4(3), MoMo′ 3.2109(4), MoP 2.4567(8), PC(8) 1.834(3), PH(P) 1.37(3) Å). 相似文献
14.
《Journal of organometallic chemistry》1986,299(2):213-221
We report the synthesis and characterisation of binuclear η5-pentamethylcyclopentadienylrhenium complexes, [(η5-C5Me5)Re(CO)2]2(μ-E) (E = S (2), Se (3), Te (4)), containing a chalcogen bridge in addition to a ReRe bond. According to the X-ray structural analysis, 3 possesses approximately C2 molecular symmetry; the C5Me5 ring ligands occupy trans positions with respect to the central Re2Se unit [d(ReRe) 3.032(1) Å, ∢ ReSeRe 74.9(1)°]. As expected, the complexes of the now complete series [CpRe(CO)2]2(μ-E) (E = O (1), S (2), Se (3), Te (4)) show a high degree of similarity in their corresponding mass, IR, 1H and 13C NMR spectra. 相似文献
15.
《Analytical letters》2012,45(5):309-316
Abstract In fluorosulfuric acid, four different sulfur species: S2 +., S+., S(II+), S(IV+), 3 different selenium species: Se2 +., Se(II+), Se(IV+), and 3 different Tellurium species: Te2 2+, Te(II+) and Te(IV+) have been observed spectrophotometrically and electrochemically by varying the composition of the solvent from basic (non-oxidizing) medium (0.1M solution of NaSO3F) to oxidizing media (0.5M solution of SO3). 相似文献
16.
《Polyhedron》1986,5(9):1459-1465
The new ionic complexes [PtMe3{MeE(CH2)nE′(CH2)nEMe}]+X− [n = 3; E = E′ = S : n = 2; E = Se or S; E′ = O, S, Se or SS: X = I, BPh4 or BF4] and [PtMe3(H2NCH2CH2)2E′]+BF−4 [E′ = O or SS] have been prepared and characterized by molar-conductivity measurements and 1H NMR spectroscopy. The hitherto unreported ligands [(MeE(CH2)n)2E′] (n = 3; E = E′ = S: n = 2; E = Se; E′ = O or S or Se: n = 2; E = S; E′ = Se] have been characterized by 1H NMR and 77Se NMR (where appropriate), and by mass spectroscopy. 相似文献
17.
R. Mercier J.P. Malugani B. Fahys J. Douglande G. Robert 《Journal of solid state chemistry》1982,43(2):151-162
The crystalline compound Li4P2S6 is obtained either by devitrification of Li4P2S7 glass at 450°C with sulfur formation or by crystallisation at 450°C of a Li2S, P and S melt. The structure determination has been solved by X-ray diffraction on a monocrystal. The unit cell is hexagonal with a = 6.070(4), c = 6.577(4) Å, V = 209 Å3, Z = 1. Intensities were collected at 293°K with Kα (λ = 0.71069 Å) Mo radiation on an automatic Nonius CAD-4 diffractometer. The structure was solved under the assumption of random disorder of P atoms over two sites (occupancy factor of 0.5). Anisotropic least-squares refinement with W = 1 gave R = 0.047 for 90 independent reflections and 9 variables. The structure is built according to an ABAB sequence sulfur packing. Per unit cell, four out of six octahedral sites are occupied by Li ions, and the other two are statistically filled (0.5) by PP pairs. The PP central bond (2.256(13) Å) links two staggered PS3 groups (PS = 2.032(5) Å) to form the D3d symmetry P2S4?6 anion. Infrared and Raman spectra show features very similar to those of Na4P2S6, 6H2O and MIIPS3 compounds. A new assignment in terms of symmetry species is proposed for the P2S6 internal modes, which is confirmed by a normal coordinate calculation using a valence force field; the stretching force constants fPP and fPS are equal to 1.6 and 2.7 mdyne Å?1, respectively. 相似文献
18.
Martin Minelli J.H. Enemark Andrew Bell Richard A. Walton 《Journal of organometallic chemistry》1985,284(1):25-34
The 95Mo NMR spectra of a series of seven-coordinate molybdenum(II) isocyanide complexes of the types [Mo(CNR)7-nLn](PF6)2 (R = CH3, CHMe2, CMe3, C6H11, CH2Ph; L = py, bpy, Me2bpy, phen, dppe, P-n-Bu3; n = 0,1,2) [Mo(CNC-Me3)6X]PF6 (X = Cl, Br, I) and [{Mo(CNCMe3)4(NN)}2(μ-CN)](PF6)3 (NN = bpy, Me2bpy, phen) have been studied. The 95Mo chemical shift range for this group of complexes is about 1100 ppm. An increase in the size of the R group attached to the isocyanide ligand generally tends to shield the 95Mo nucleus. Replacement of the isocyanide ligand with a phosphorus ligand also increases the shielding, whereas the replacement of isocyanide with a heterocyclic nitrogen donor leads to deshielding by 800–900 ppm. This group of complexes shows a normal halogen dependence, i.e. replacement of Cl? by Br? and I? increases the shielding of the 95Mo nucleus. The cyano-bridged cations [{Mo(CNCMe3)4(NN)}2(μ-CN)]3+ (NN = bpy, Me2bpy, or phen) show two 95Mo NMR signals, one for the molybdenum coordinated to the carbon of the bridging CN and one for the N-coordinated molybdenum. Comparison of the chemical shifts and linewidths of the cyano-bridged species with those of the corresponding mononuclear molybdenum(II) complexes [Mo(CNCMe3)5(NN)](PF6)2 leads to the assignment of the more deshielded signal to the N-coordinated molybdenum. The 14N and 31P NMR spectra for these complexes have also been measured, as have the 13C NMR spectra of the pairs of complexes [Mo(CNCMe3)5(NN)](PF6)2 and [{Mo(CNCMe3)4(NN)}2(μ-CN)](PF6)3 (NN = bpy or phen). The 183W NMR spectra for [W(CNR)5(bpy)](PF6)2 (R = CMe3 and CH2Ph), show that the δ(183W)/δ(95Mo) chemical shift ratios for isocyanide complexes are different from the ratio found for M0 and MVI. 相似文献
19.
A. L. Gushchin M. R. Ryzhikov A. V. Virovets M. N. Sokolov 《Russian Journal of Coordination Chemistry》2013,39(2):181-186
High-temperature reactions of Mo, chalcogen (S or Se), Te, and Br2 in molar ratio Mo: S/Se: Te: Br = 3: 1: 6: 4 were carried out. The reaction products were subjected to mechanochemical activation with K(Dtp) (Dtp = (EtO)2PS2) in a vibrational mill, resulting in the formation of new compounds [Mo3(μ3-Q)0.5(μ3-O)0.5(μ2-Te2)3(Dtp)3](Dtp) (Q = Se (I) and S (II)). The structure of compound I has been established by X-ray diffraction analysis. Solutions of compounds I and II contain mixtures of [Mo3(μ3-Q)(μ2-Te2)3(Dtp)3]+ and [Mo3(μ3-O)(μ2-Te2)3(Dtp)3]+, which is confirmed by mass spectrometry and 31P, 77Se, and 125Te NMR spectroscopy. Quantum-chemical calculations of the 125Te NMR chemical shifts were performed. The compounds are also characterized by IR spectroscopy, Raman spectroscopy, and elemental analysis. Structure I contains short nonvalent contacts between the sulfur atom of the out-of-sphere Dtp anion and the axial tellurium atoms of the cluster. 相似文献
20.
This paper reports equilibrium phase data for the manganese-containing system Mn0.394Ti0.606OS. The system was studied at 1380 and 1485°K by an equilibration and quench technique. The oxygen and sulfur fugacities of the equilibrating gas atmosphere were independently controlled using mixtures of the three gases hydrogen, carbon dioxide, and hydrogen sulfide. The results are presented on log fS2 vs log fO2 phase diagrams which are discussed in terms of the equilibria between manganese in the oxide phases and manganese in the α-MnS sulfide phase. The results are shown to be consistent with previously published data for the subsystems MnTiO, MnOS, MnS, and TiOS. 相似文献