- Synthesis and characterization of molybdenum disulphide formed from ammonium tetrathiomolybdate
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An investigation has been carried out into the possibility of in situ formation of MoS2 within porous anodic films on aluminium, to improve subsequent tribological behaviour, by re-anodizing in thiomolybdate electrolyte. Acidification of thiomolybdate was employed to simulate the conditions for formation of the sulphide at the anodic film/electrolyte interface, followed by appropriate vacuum heat treatments to study possible temperature effects on the sulphide due to either friction or Joule heating during anodizing. The products of both acidification and heat treatment, characterized by X-ray powder diffraction and scanning electron microscopy, were compared with those formed by direct thermal decomposition of ammonium tetrathiomolybdate crystals. The precipitate formed by acidification was mainly amorphous molybdenum trisulphide (MoS3), which on heat treatment at 450 and 850°C yielded 3R-MoS2. 3R-MoS2 also formed by the thermal decomposition of thiomolybdate crystals. Thermogravimetric and differential thermal analyses showed that the decomposition of MoS3 to MoS2 occurred in the range 220-370°C and revealed the sequence of reaction steps. The findings suggest that mainly amorphous MoS3 is formed as a consequence of changes in the pH of the film/electrolyte interface during re-anodizing but the product is relatively easily transformed to crystalline MoS2 on moderate heating which may occur during wear processes.
- Wang,Skeldon,Thompson,Wood
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- Electron Spin Resonance of Paramagnetic Species as a Tool for Studying the Thermal Decomposition of Molybdenum Trisulfide
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ESR has been used in the study of the irreversible thermal decomposition of molybdenum trisulfide to disulfide in the range 180-600 deg C.Three paramagnetic species were observed: (a) MoS3+, whose magnetic parameters were different depending on which phase, either MoS3 or MoS2, was predomonant; (b) sulfur chain radical, due to loss of sulfur during the decomposition; (c) MoO3+, due to a very low degree of contamination of the system with oxygenated Mo species.The nature of these species is discussed.The intensity and the line shape of signals for a and b as a function of the treatment temperature of the samples were used to follow the decomposition steps.The ESR results have been correlated with X-ray and analytical data.
- Busetto, Luigi,Vaccari, Angelo,Martini, Giacomo
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- The influence of reducing and sulfiding conditions on the properties of unsupported MoS2-based catalysts
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Unsupported MoS2 catalysts were obtained from the decomposition of ammonium tetrathiomolybdate (ATM) at variable temperatures (400-700 °C) and under different gas compositions, from pure H2S to pure H2. The catalysts were further studied in the non-promoted state or promoted by Ni and Co. Catalytic activity and selectivity were studied in the model reaction of thiophene hydrodesulfurization (HDS). Surface areas, crystalline phase and particle size distributions were determined by Brunauer-Emmet-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. A comparison of average values calculated from these techniques has enabled the understanding of the morphology of the solids. The catalysts were characterized before and after catalytic tests by X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS) and temperature-programmed reduction (TPR). Comparison of catalytic activity trends with the results of the characterizations show that over-stoichiometric sulfur, present in the fresh catalysts in the form of edge-located S22 - species, plays a key role for the activity of unsupported MoS2 and for its ability to be promoted. Direct hydrogenation (HYD) of thiophene to butane occurs presumably with the participation of -SH groups, produced from the opening of S-S bridges by hydrogen. Whatever the gas atmosphere, any treatment leading to the removal of over-stoichiometric sulfur leads to a decrease in HYD selectivity. Thus, very similar catalytic properties were observed for MoS2 annealed at 700 °C in pure H2, H2S or N2 gases. Ni and Co introduced by means of reflux with acetylacetonates, gave identical promotion trends for all the MoS2 samples. The solids treated in pure H2S could not take up promoter atoms at the edges, whereas for the H2-reduced samples high promotion levels were achieved. The degree of stacking does not seem to have a significant impact on the thiophene HDS activity and selectivity of the unsupported MoS2 catalysts.
- Afanasiev, Pavel
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- Lineshapes of ESR signals and the nature of paramagnetic species in amorphous molybdenum sulfides
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Amorphous and poorly crystallized molybdenum sulfides were studied by ESR. Qualitative analysis of the spectra suggested the presence of three paramagnetic species. A simulation of the ESR spectra was attempted. ESR lines were determined over the stoichiometric range MoS3 → MoS2. A good representation of the main part of the experimental lines was obtained. There was no significant variation of the g values of the various components of the spectra during the transformation from Mo3to Mo2. The first signal was attributed to sulfur centers. The other two signals were assigned to metal centers.
- Deroide,Bensimon,Belougne,Zanchetta
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- SYNTHESIS OF NOVEL MOLYBDENUM CHALCOGENIDES.
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Recently, there has been substantial interest in using molybdenum chalcogenides as active cathodes in lithium batteries. It has been observed that the structural make-up of the material (crystalline or amorphous) is often of critical importance in the abi
- Schleich,Martin
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- Aqueous solution processed MoS3as an eco-friendly hole-transport layer for all-inorganic Sb2Se3solar cells
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Here we report a solution processed environmentally friendly MoS3 hole-transport material for Sb2Se3 solar cells, where MoS3 exhibits a matched energy level relative to Sb2Se3. In the synthesis, H2S produced by the thermal decomposition of (NH4)2MoS4 is found to efficiently eliminate the antimony oxide impurity formed on the Sb2Se3 surface. Finally, the all-inorganic Sb2Se3 solar cell delivers an efficiency of 6.86% with excellent stability. This journal is
- Ma, Yuyuan,Yin, Yiwei,Li, Gang,Lian, Weitao,Zhang, Jianwang,Tang, Rongfeng,Ju, Huanxin,Chen, Tao
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- Simple solution route to uniform MoS2 particles with randomly stacked layers
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MoS2 particles of uniform size (ca. 70nm) consisting of random and loosely stacked layers have been synthesized from hydrazine solution with (NH4)2Mo3S13 as the precursor at 180°C for 16h under hydrothermal conditions. The particles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HREM). The influences of reaction conditions are discussed while a mechanism is proposed to explain the formation of this peculiar morphology.
- Li, Qing,Li, Ming,Chen, Zhiqian,Li, Chunmei
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- MoS3 thin film cathodes prepared by chemical vapor deposition
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Amorphous molybdenum trisulfide (MoS3) is a promising candidate as a host material in a lithium insertion battery. Thin films of MoS3 have been prepared by chemical vapor deposition from molybdenum hexafluoride (MoF6) and hexamethyldisilthiane (HMDST). Continuous, adherent films were obtained at deposition temperatures in the range of 150° to 400°C on aluminum, nickel, silica, and alumina substrates. Infrared analyses indicate that deposition temperatures between 200° and 250°C produce the purest films. The best electrochemical performance was achieved on films deposited in the range of 210°C to 240°C, which corresponded to those films analytically determined to be MoS3.
- Schleich,Chang,Barberio,Hanson
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- Formation and catalytic properties of edge-bonded molybdenum sulfide catalysts on TiO2
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The effect of preparation conditions (calcination atmosphere, sulfidation atmosphere, and sulfidation temperature) on the orientation of MoS2 clusters on TiO2 supports was studied. Edge-bonded MoS2 clusters formed when the catalyst was sulfided in a flow of H2S/N2 at 573 or 673 K. However, when sulfided in H2S/N2 at higher temperatures than 773 K, the edge-bonded MoS2 clusters transformed to highly aggregated basal-bonded MoS2 clusters. Catalytic activity tests, using hydrogenation of 1-methylnaphthalene as a model test reaction, revealed that the turnover frequency on the catalyst with edge-bonded MoS2 clusters prepared by sulfiding at 573 K in H2S/N2 was higher than that on the catalyst with basal-bonded MoS2 clusters prepared by sulfiding in H2S/H2.
- Araki, Yasuhiro,Honna, Kosaku,Shimada, Hiromichi
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- Electron Spin Resonance of Water Adsorption on Amorphous Molybdenum Sulfide
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The interaction between molybdenum trisulfide and water vapor has been studied by ESR.The trisulfide was obtained from the thermal decomposition of (NH4)2MoS4.The observed spectra are characteristic of two distinct paramagnetic species.The first one corre
- Bensimon, Y.,Belougne, P.,Giuntini, J. C.,Zanchetta, J. V.
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- Synthesis, spectroscopic, thermal and X-ray structure characterization of 1,3-propanediammonium tetrathiomolybdate and N,N,N′,N′- tetramethylethylenediammonium tetrathiomolybdate
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The title compounds 1,3-propanediammonium tetrathiomolybdate, 1, and N,N,N′,N′-tetramethylethylenediammonium tetrathiomolybdate, 2, were prepared by reacting the ammonium salt of [MoS4]2- with the corresponding organic diamine. The two diamines have different steric bulk and different numbers of potential hydrogen-bonding donors. This results in different crystal packings viz. a three-dimensional network in 1 and isolated groups consisting of two cations and two anions in 2. The title compounds 1,3-propanediammonium tetrathiomolybdate, (1,3-pnH2)[MoS 4], 1 and, N,N,N′,N′-tetramethylethylenediammonium tetrathiomolybdate, (tmenH2)[MoS4], 2, were prepared by reacting the ammonium salt of [MoS4]2- with the corresponding organic diamine. In 1 and 2 the organic diamines 1,3-propanediamine (1,3-pn) and N,N,N′,N′-tetramethylethylenediamine (tmen) are present in their diprotonated form. The reaction of 1 or 2 with [Ni(en)3]Cl2 ? 2H2O (en is ethylenediamine) results in the formation of the highly insoluble complex tris(ethylenediamine)Ni(II) tetrathiomolybdate, [Ni(en)3][MoS 4], in quantitative yields. 1 and 2 have been characterized by chemical analysis, vibrational, UV-Vis and NMR spectroscopy, TG-DTA-MS and single crystal X-ray crystallography. Compound 1 is thermally more stable compared to 2. Both complexes decompose in a single step forming amorphous molybdenum sulfide. The structure of the title complexes can be described as consisting of tetrahedral [MoS4]2- dianions which accept a complex series of H-bonds from the organic dications. The strength and number of these hydrogen bonds affect the Mo-S bond lengths.
- Srinivasan, Bikshandarkoil R.,Dhuri, Sunder N.,N?ther, Christian,Bensch, Wolfgang
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- New synthesis route of PbMo6S8 superconducting Chevrel phase from ultrafine precursor mixtures: I. PbS, MoS2 and Mo powders
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Fine powders of PbMo6S8 Chevrel phase (approximately 0.5 μm) obtained from new ultrafine precursor powders present excellent intrinsic superconducting properties, such as a critical temperature, Tc, of about 14 K. These results are due to ultrafine quasi-spherical PbS, MoS2, and Mo precursor powders (0.05-0.5 μm) of lead Chevrel phase synthesized by soft chemistry methods (precipitation, co-precipitation). Thus, a better reactivity between the grains of the mixture allows a decrease in the synthesis temperature of the resulting PbMo6S8 phase (800 °C instead of 950-1000 °C) required for the PbMo6SS8 synthesis from the same precursor powders made by the classical ceramic route. These new Chevrel phase powders have very fine homogeneous grains with high potential surface reactivity, giving improved grain boundaries that are able to carry high current densities.
- Even-Boudjada,Burel,Chevrel
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- One-step liquid phase chemical method to prepare carbon-based amorphous molybdenum sulfidesAs the effective hydrogen evolution reaction catalysts
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Two different kinds of carbon-based amorphous molybdenum sulfide composite catalysts (activated carbon supported amorphous molybdenum sulfide and acetylene black supported amorphous molybdenum sulfide) had been prepared in a facile and scalable one-step liquid phase chemical method. The morphological and structural information of catalysts was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and it's electro-catalytic HER activity were evaluated by linear sweep voltammetry(LSV), amperometric i-t technology and AC impedance technology. The as-prepared carbon-based amorphous molybdenum sulfides showed greatly enhanced electro-catalytic activity for HER compared with pure amorphous molybdenum sulfides. Especially, the nano-sized acetylene black supported molybdenum sulfide exhibited excellent electro-catalytic HER performances with a low onset potential of ?116?mV versus reverse hydrogen electrode (RHE) and a small Tafel slope of 51?mV per decade.
- Guo, Mengmeng,Wu, Qikang,Yu, Miaomiao,Wang, Yinling,Li, Maoguo
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- Micelle-assisted fabrication of necklace-shaped assembly of inorganic fullerene-like molybdenum disulfide nanospheres
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The fabrication of necklace-shaped assembly of inorganic fullerene-like molybdenum disulfide nanospheres via a micelle-assisted route is reported, in which necklace-shaped assembly of amorphous MoS3 nanospheres is driven by the aggregation transformation of surfactants at low temperatures and then is transformed to the assembly of target fullerene-like MoS2 by annealing. This nanostructure is a type of oriented assembly of inorganic fullerene-like structures, which is confirmed by the transmission electron microscopy and high-resolution transmission electron microscopy analysis. The optical absorption property is investigated to show their inorganic fullerene-like structure and uniform shape.
- Xiong, Yujie,Xie, Yi,Li, Zhengquan,Li, Xiaoxu,Zhang, Rong
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- Mo K-Edge EXAFS and S K-Edge Absorption Studies of the Amorphous Molybdenum Sulfides MoS4.7, MoS3, and MoS3.nH2O (n .apprx. 2)
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Molybdenum K-edge EXAFS measurements on the new amorphous sulfide, MoS4.7, and the known amorphous sulfides, MoS3 and MoS3.nH2O (n .apprx. 2), have yielded information on the coordination around molybdenum in these compounds. The results for MoS3 and its hydrates, MoS3.nH2O (n = 1.7, 2.1, and 2.2), prepared using a number of different methods, show that thecoordination around molybdenum is the same in all of these materials. In MoS3 and MoS3.nH2O, molybdenum is surrounded by six sulfurs at .apprx.2.43 ? and is also bonded to a molybdenum at 2.76 ?. No evidence was found for the longer Mo-Mo distance of .apprx. 3.2 ? in MoS3 which has been reported by other workers. There is evidence that the Mo-Sbond lengths are inequivalent but not as markedly different as has beensuggested previously. Our results suggest that the models for MoS3 presented in the literature to date may be incorrect. The local structure around molybdenum in MoS4.7 differs from that in MoS3. The most important differences are that the average number of sulfur atoms around each molybdenum in MoS4.7 is higher than in MoS3 and that the Mo-Mo coordination number is greater. Our structural model for MoS4.7 takes account of thiswith an average 7 1/3 sulfurs around each molybdenum and an average Mo-Mo coordination number of 1 1/3. EXAFS analysis and infrared spectroscopy are consistent with the formulation of MoS3 as Mo(V)(S(2-))2(S2(2- ))0.5 and MoS4.7 as Mo(4.7)(S2(2-))2.35. Sulfur K-edge absorption spectra for MoS3, MoS4.7, sulfur, and the model compound VS4 are in agreement with these formulations and assignment of oxidation states. Comparisons with crystalline materials are made and possible models of the structures presented.
- Hibble, Simon J.,Rice, David A.,Pickup, David M.,Beer, Michael P.
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- 2D amorphous MoS3 nanosheets with porous network structures for scavenging toxic metal ions from synthetic acid mine drainage
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This is the first time that two-dimensional (2D) amorphous MoS3 nanosheets were prepared by the exfoliation of the bulk amorphous MoS3 material in dimethylformamide (DMF) solvent under ultrasonic irradiation. The obtained 2D amorphous MoS3 nanosheets show a unique porous network structure, which is quite different from that of 2D crystalline MoS2 nanosheets. The XPS and Raman results reveal that the structure of 2D amorphous MoS3 nanosheets contains high levels of active sulphide groups with unsaturated bonds, suggesting that this material can be applied as an efficient heavy metal scavenger in the field of environmental remediation. The interaction mechanisms between metal ions and specific sulphide groups on 2D amorphous MoS3 nanosheets have been discussed. The feasibility of toxic metal remediation (Cu, Cd and Hg) from a synthetic acid mine drainage solution has been proven. The results suggest that 2D amorphous MoS3 nanosheets as a new member of the 2D material family will have promising applications in environmental protection.
- Fu, Weng,Yang, Siyuan,Yang, Hong,Guo, Bao,Huang, Zhiqiang
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supporting information
p. 18799 - 18806
(2019/08/20)
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- MoS2 formation induced by amorphous MoS3 species under lubricated friction
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Amide molybdate has been recently introduced as a friction modifier for tribological applications. Combined with zinc dithiophosphate (ZDDP) and fatty amines, it provides an ultralow friction coefficient. The ultimate product of Mo compound transformations in tribological contact, due to frictional heating and shearing, as well as chemical interactions with oil additives, is molybdenum sulfide (MoS2). Understanding the decomposition of amide molybdate leading to MoS2 is of primary importance to the optimization of the design of lubricant formulations. This study focuses on the investigation by Raman spectroscopy of amide molybdate decomposition intermediates. Raman spectra of tribofilms, obtained after friction tests under different temperatures and pressures, revealed the formation of an amorphous MoS3 intermediate coexisting with MoS2. However, under severe conditions, the tribofilms are mostly composed of MoS2.
- Oumahi,De Barros-Bouchet,Le Mogne,Charrin,Loridant,Geantet,Afanasiev,Thiebaut
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p. 25867 - 25872
(2018/08/04)
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- The sequential continuous-flow hydrothermal synthesis of molybdenum disulphide
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Molybdenum disulphide (MoS2) has been widely used as a catalyst and high temperature lubricant. It has been heavily researched recently as a graphene analogue and member of the so-called inorganic fullerenes. Here we report the first continuous flow hydrothermal synthesis of MoS2. With fast reaction times and flexibility the continuous flow hydrothermal system allowed MoS2 to be produced in a stepwise fashion, offering an insight into the mechanism involved. It has been found that the synthesis of MoS2 proceeded via the sulphidation of molybdate anions to thiomolybdate species, which are transformed to amorphous MoS3 by acidification in flow, before further hydrothermal treatment decomposes this amorphous precursor to tangled MoS2 nanosheets. This journal is
- Dunne, Peter W.,Munn, Alexis S.,Starkey, Chris L.,Lester, Edward H.
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p. 4048 - 4050
(2015/04/14)
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- Growth and activation of an amorphous molybdenum sulfide hydrogen evolving catalyst
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Amorphous molybdenum sulfide films, prepared by electrodeposition, are a class of highly active catalysts for hydrogen evolution. The growth mechanism of the films and the true active species were unclear. Herein, we report a study of the growth and activation of these films using Electrochemical Quartz Crystal Microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS). Three processes, including oxidative deposition, reductive corrosion, and reductive deposition, are occurring during the growth of a molybdenum sulfide film. Deposition method, precursor concentration, and potential window are among the factors influencing the film growth. Regardless of deposition methods, all films exhibit similar catalytic activity on a per mass base. Potentiostatic oxidation (anodic electrolysis) is the method for fastest film growth; it produces a MoS3 film precatalyst which can be electrochemically activated. The activity of the MoS3 precatalyst scales with catalyst loading; at a loading of 0.2 mg/cm2, the current density is 20 mA/cm2 at an overpotential of 170 mV. Films differently deposited have different initial compositions, but the active catalysts in all films are the same MoS 2+x species, whose XPS characteristics are distinct from those of crystalline MoS2. The activation process of a MoS3 film precatalyst involves a reductive removal of slightly less than one equivalent of sulfide to form MoS2+x.
- Vrubel, Heron,Hu, Xile
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p. 2002 - 2011
(2013/09/24)
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- Heterobinuclear cobalt-oxomolybdenumthiocyanate complexes of dithiocarbamates or 8-quinolinol
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The heterobinuclear complexes of [CoMoO2(NCS)(L) 3(H2O)] (L=diethyldithiocarbamate, 4-morpholinyldithiocarbamate or 8-quinolinol) are prepared by the interaction of ammonium molybdate with ammonium thiocyanate in the presence of hydrazinium sulphate and cobalt(II) nitrate with the respective ligands in DMF. The magnetic moment, EPR and PES data suggest the presence of molybdenum(V) and low-spin cobalt(III). The crystal field splitting parameters have been evaluated from the electronic spectral data. The infrared spectra suggest the presence of N-bonded thiocyanate ligand (2040 and 780 cm-1), dithiocarbamate ligands (1500 and 960 cm-1) and (Mo=O) (910 cm -1) in the molecule. The extensive splitting in each peak observed in the 1H NMR spectra of the complexes indicate the restricted rotation of the alkyl side chain of the bidentate dithiocarbamate groups. The redox behaviour of the complexes in DMF is discussed from the cyclic voltammetry data. The thermal decomposition and infrared spectral studies confirm the presence of coordinated water molecule. The proposed structure consists of an octahedral cobalt(III) and an octahedral oxomolybdenum(V) bridged by an oxo and a thiocyanate groups.
- James,Nagaraja
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p. 1900 - 1904
(2007/10/03)
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- New low-temperature synthesis of transition-metal sulfides
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The reaction of hexamethyldisilthiane with transition-metal halides at room temperature results in the rapid synthesis of transition-metal Sulfides. Sulfides that are normally difficult or even impossible to produce by using classical methods are readily produced. This method allows great control of reaction conditions and can be used with a wide range of transition metals and oxidation states. The sulfides that are synthesized are anhydrous, unlike those produced by many other low-temperature methods. This is a concern in applications such as the use of the materials as cathodes in secondary lithium batteries. The reactions were fast and usually exothermic, producing sulfides that were amorphous to X-ray diffraction. The only coproducts of the reaction between hexamethyldisilthiane and the metal halides are trimethylsilyl halides. These compounds are all volatile liquids and are easy to separate from the sulfides produced. Retention of the formal oxidation state of the metal from the halide was found in the sulfide in all cases.
- Martin, Michael J.,Qiang, Guo-Hua,Schleich, Donald M.
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p. 2804 - 2808
(2008/10/08)
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