Reaction Of MoO3 Research Articles

Discrete Arsonate-Grafted Inverted-Keggin 12-Molybdate Ion [Mo12O32(OH)2(4-N3C2H2-C6H4AsO3)4]2- and Formation of a Copper(II)-Mediated Metal-Organic Framework.

The discrete inverted-Keggin ion [Mo12O32(OH)2(4-N3C2H2-C6H4AsO3)4]2- (1) has been prepared in an aqueous acidic (pH 0.8) medium by the reaction of MoO3 with the (4-triazolylphenyl)arsonic acid 4-N3C2H2-C6H4AsO3H2 under hydrothermal conditions and was isolated as a sodium salt in 21% yield. The exact same reaction in the presence of Cu2+ ions resulted in the neutral metal-organic framework (MOF) Cu2[Mo12O34(4-N3C2H2-C6H4AsO3)4] (Cu-1) in 68% yield. The inverted-Keggin ion 1 comprises a metal-oxo core, which is capped by four organoarsonate groups, and in Cu-1, individual polyanions are linked in the solid state by coordination of the Cu2+ ions with the triazolyl groups. The discrete ion 1 was characterized by single-crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic absorption (AA) spectroscopy, as well as thermogravimetric analysis (TGA), and the POM-MOF Cu-1 was characterized by single-crystal and powder XRD, FT-IR, TGA, and gas sorption. Cu-1 has channels with a diameter of around ∼0.9 nm and exhibits a water-vapor adsorption capacity of 89.7 cm3 g-1 (p/p0 = 0.95).

Solvothermal synthesis of potassium, rubidium, and cesium molybdenum oxyfluorides

Attention has recently been paid to oxyfluorides, one of the mixed anion materials, because they possess unique properties for many kinds of application fields. Because the general synthesis processes for oxyfluorides are based on troublesome methods, novel safe and facile processes are required. In this study, MoO3 was solvothermally reacted with KF, RbF, and CsF at 200 °C to form potassium, rubidium, and cesium molybdenum oxyfluorides. The reaction of MoO3 with KF and RbF led to the formation of K3MoO3F3 and Rb3MoO3F3 with a known structure, respectively, while the reaction of MoO3 with CsF induced an unknown phase which should be Cs3MoO3F3 with the similar structure to those of K3MoO3F3 and Rb3MoO3F3. A3MoO3F3 (A = K, Rb, and Cs) has not been synthesized under liquid phase until now, and this research clarified this kind of the solvothermal reaction can lead to the formation of unique oxyfluorides at low temperature. In addition, Cs3MoO3F3 was converted into Cs3Mo2O6F3 by treatment with methanol, suggesting the instability of Cs3MoO3F3. This kind of conversion reaction from one oxyfluoride to the other oxyfluoride has not been reported, and the development of such chemical conversion may lead to the formation of new oxyfluorides.

Catalytic oxidation of benzyl-alcohol with H2O2 in the presence of a dioxidomolybdenum(VI) complex

A new dioxidomolybdenum(VI) complex, [MoO2(L)(CH3OH)] (1), was synthesized by the reaction of MoO3 with ONO-donor hydrazone ligand that is obtained from the condensation of benzolyacetone and furan-2-carbohydrazide in methanol. Both of the ligand and complex were characterized by elemental analysis and FT-IR, NMR and UV–Vis spectroscopic methods. The structure of complex was also determined by single crystal X-ray analysis. Structural analysis showed that the Mo(VI) ion has a distorted octahedral geometry and the ligand is coordinated to the metal ion as dinegative ONO-donor ligand. The obtained molybdenum(VI) complex was used as catalyst in oxidation of benzyl alcohol with H2O2 as a green oxidant. The effects of some parameters such as temperature, solvent and ratio of materials were also studied. Catalytic studies indicated that complex 1 can efficiently catalyze the oxidation of benzyl alcohol but its activity and selectivity are considerably dependent on the reaction condition.

Vanadium(V) and Molybdenum(VI) Complexes Containing ONO Tridentate Schiff Bases and Their Application as Catalysts for Oxidative Bromination of Phenols

AbstractCondensation of 2,4‐dihydroxyacetophenone with isonicotinoyl hydrazide and nicotinoyl hydrazide in an equimolar ratio in methanol results in the formation of two stable ONO donor ligands, H2dhap‐inh (I) and H2dhap‐nah (II), respectively. These ligands react with [VIVO(acac)2] (Hacac=acetylacetone) in 1:1 molar ratio to give the corresponding neutral dioxidovanadium(V) complexes, [VVO2(Hdhap‐inh)] (1) and [VVO2(Hdhap‐nah)] (2), after overnight aerial oxidation in the presence of K2CO3. In the absence of K2CO3, they result in (μ‐O){bisoxidovanadium(V)} complexes, [{VVO(dhap‐inh)}2(μ‐O)] (3) and [{VVO(dhap‐nah)}2(μ‐O)] (4). Treatment of neutral dioxidovanadium(V) complexes,1and2, with H2O2yields oxidoperoxidovanadium(V) complexes K[VVO(O2)(dhap‐inh)(H2O)] (5) and K[VVO(O2)(dhap‐nah)(H2O)] (6). The ligands also react with [MoVIO2(acac)2] in 1:1 molar ratio to form [MoVIO2(dhap‐inh)]n(7) and [MoVIO2(dhap‐nah)]n(8). The reaction of oxidoperoxidomolybdenum(VI) species, generated in situ by the reaction of MoO3with H2O2with ligandsIandII, gives the oxidoperoxidomolybdenum(VI) complexes, [MoVIO(O2)(dhap‐inh)(MeOH)] (9) and [MoVIO(O2)(dhap‐nah)(MeOH)] (10), respectively. All synthesized complexes are characterized by elemental analysis, thermogravimetric, electrochemical, spectroscopic (IR, UV–Vis,1H,13C and51V NMR) and single crystal X‐ray diffraction (for1,2and8). Complexes are explored as catalysts for the oxidative bromination of phenol, a model oxidative halogenation reaction, in the presence of HClO4and KBr, using 30% H2O2as oxidant. Under optimized reaction conditions, the product selectivity follows the order: 4‐bromophenol>2‐bromophenol, both for molybdenum and vanadium complexes. Products characterized by GC analysis showed very good conversion of phenol.

Nanosheets of MoOx crystallites synthesized via chemical vapor deposition and its potential in bolometric applications

The various oxidation levels of molybdenum oxide have attracted attention in recent years due to their interesting optical and electrical properties as a function of the oxygen vacancy and stoichiometry. Specifically, the substoichiometric MoOx (2 < x < 3) behaves as a high work function conductor, based on its metallic defect band. As a result, one of the potential applications of MoOx includes a contact material for high hole injection or extraction. Another advantage of MoOx is its chemical stability and high conductivity. In this work, we have synthesized MoOx nanosheets via chemical vapor deposition by the reaction of MoO3 with S powder precursors and N2 as the transport gas. Several characterization techniques were carried out in our material to measure the quality, topography, and composition of our samples, including AFM, SEM, and Raman spectroscopy. Additionally, a four-terminal device was fabricated via e-beam lithography and electrically characterized as a function of temperature. Outstanding properties were obtained from our material, including a high conductivity of ∼6,680.3 S cm−1, a superior temperature coefficient of resistance of ∼ −0.10%, and high sensitivity based on the bolometric coefficient of 0.152 mS K−1.

First principle study of formation mechanism of molybdenum-doped amorphous silica in MoO&lt;sub&gt;3&lt;/sub&gt;/Si interface

An amorphous mixing layer (3.5–4.0 nm in thickness) containing silicon (Si), oxygen (O), molybdenum (Mo) atoms, named &lt;i&gt;α&lt;/i&gt;-SiO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;(Mo), is usually formed by evaporating molybdenum trioxide (MoO&lt;sub&gt;3&lt;/sub&gt;) powder on an n-type Si substrate. In order to investigate the process of adsorption, diffusion and nucleation of MoO&lt;sub&gt;3&lt;/sub&gt; in the evaporation process and ascertain the formation mechanism of &lt;i&gt;α&lt;/i&gt;-SiO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;(Mo) on a atomic scale, the first principle calculation is used and all the results are obtained by using the Vienna &lt;i&gt;ab initio&lt;/i&gt; simulation package. The possible adsorption model of MoO&lt;sub&gt;3&lt;/sub&gt; on the Si (100) and the defect formation energy for substitutional defects and vacancy defects in &lt;i&gt;α&lt;/i&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; and &lt;i&gt;α&lt;/i&gt;-MoO&lt;sub&gt;3&lt;/sub&gt; are calculated by the density functional theory. The results show that an amorphous layer is formed between MoO&lt;sub&gt;3&lt;/sub&gt; film and Si (100) substrate according to &lt;i&gt;ab initio&lt;/i&gt; molecular dynamics at 1500 K, which are in good agreement with experimental observations. The O and Mo atoms diffuse into Si substrate and form the bonds of Si—O or Si—O—Mo, and finally, form an &lt;i&gt;α&lt;/i&gt;-SiO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;(Mo) layer. The adsorption site of MoO&lt;sub&gt;3&lt;/sub&gt; on the reconstructed Si (100) surface, where the two oxygen atoms of MoO&lt;sub&gt;3&lt;/sub&gt; bond with two silicon atoms of Si (100) surface, is the most stable and the adsorption energy is －5.36 eV, accompanied by the electrons transport from Si to O. After the adsorption of MoO&lt;sub&gt;3&lt;/sub&gt; on the Si substrate, the structure of MoO&lt;sub&gt;3&lt;/sub&gt; is changed. Two Mo—O bond lengths of MoO&lt;sub&gt;3&lt;/sub&gt; are 1.95 Å and 1.94 Å, respectively, elongated by 0.22 Å and 0.21 Å compared with the those before the adsorption of MoO&lt;sub&gt;3&lt;/sub&gt; on Si substrate, while the last bond length of MoO&lt;sub&gt;3&lt;/sub&gt; is little changed. The defect formation energy value of neutral oxygen vacancy in &lt;i&gt;α&lt;/i&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; is 5.11 eV and the defect formation energy values of neutral oxygen vacancy in &lt;i&gt;α&lt;/i&gt;-MoO&lt;sub&gt;3&lt;/sub&gt; are 0.96 eV, 1.96 eV and 3.19 eV, respectively. So it is easier to form oxygen vacancy in MoO&lt;sub&gt;3&lt;/sub&gt; than in SiO&lt;sub&gt;2&lt;/sub&gt;, which implies that the oxygen atoms will migrate from MoO&lt;sub&gt;3&lt;/sub&gt; to SiO&lt;sub&gt;2&lt;/sub&gt; and forms a 3.5–4.0-nm-thick &lt;i&gt;α&lt;/i&gt;-SiO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;(Mo) layer. As for the substitutional defects in MoO&lt;sub&gt;3&lt;/sub&gt; and SiO&lt;sub&gt;2&lt;/sub&gt;, Mo substitutional defects are most likely to form in SiO&lt;sub&gt;2&lt;/sub&gt; in a large range of Mo chemical potential. So based on our obtained results, the forming process of the amorphous mixing layer may be as follows: the O atoms from MoO&lt;sub&gt;3&lt;/sub&gt; bond with Si atoms first and form the SiO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;. Then, part of Mo atoms are likely to replace Si atoms in SiO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;. Finally, the ultra-thin buffer layer containing Si, O, Mo atoms is formed at the interface of MoO&lt;sub&gt;3&lt;/sub&gt;/Si. This work simulates the reaction of MoO&lt;sub&gt;3&lt;/sub&gt;/Si interface and makes clear the interfacial geometry. It is good for us to further understand the process of adsorption and diffusion of atoms during evaporating, and it also provides a theoretical explanation for the experimental phenomenon and conduces to obtaining better interface passivation and high conversion efficiency of solar cell.

A Linear Trinuclear Oxidodiperoxido‐molybdenum(VI) Complex with Single Triazole Bridges: Catalytic Activity in Epoxidation, Alcoholysis, and Acetalization Reactions

AbstractThe complex (Htrz)2[Mo3O6(O2)4(trz)2]⋅H2O (1), isolated from the reaction of MoO3 with H2O2 in the presence of 1,2,4‐triazole (trz), displays singular structural features such as double bridges comprising one oxido and one triazole ligand, and peripheral oxidodiperoxido‐molybdenum(VI) units. A comparative study was performed regarding the catalytic activity and stability of complex 1 and the hybrid material [MoO3(trz)0.5] (2) for the epoxidation of cis‐cyclooctene (Cy8), the alcoholysis of epoxides, and the acetalization of benzaldehyde (PhCHO). Methanol or ethanol were used as solvents and reagents for the latter two reactions. For the substrates Cy8, styrene oxide, and PhCHO, the corresponding epoxide, β‐alkoxy alcohol, and dialkyl acetal were obtained with 100 % selectivity at very high conversions. In general, 1 performed better than 2 for the different catalytic reactions. Under certain oxidant/co‐solvent conditions used for Cy8 epoxidation, 1 was converted to 2 during the reaction.

Single and Few-Layer MoS2: CVD Synthesis, Transference, and Photodetection Application

ABSTRACTTwo-dimensional layered materials, materials with weak out-of-plane van der Waals bonding and strong in-plane covalent bonding, have attracted special attention in recent years since the isolation and characterization of monolayer graphite, the graphene. The electrical bandgap in Transition Metal Di-Chalcogenides (TMDCs), non-existent in graphene, make them a good alternative family of materials for novel electronic and optoelectronic applications. 2H- MoS2, one of the most stable TMDCs, has been extensively studied, including the synthesis methods, and its potential applications in photodetection. The chemical vapor deposition (CVD) synthesis method has increased its potential over the years. The advantages of this method are scalability compared to micromechanical exfoliation, common process used in research laboratories, and the maintenance of the quality and intrinsic properties of the material compared to the liquid exfoliation methods. In this work, we synthesized high quality pristine 2H-MoS2 via atmospheric pressure chemical vapor deposition (APCVD) by vapor phase reaction of MoO3 and S powder precursors. The samples were characterized via Raman and photoluminescence (PL) spectroscopy and compared to mechanically exfoliated MoS2 crystal by measuring the full-width half maxima (FWHM) of monolayer and few-layer mesoscopic flakes. In addition, the CVD synthesized single and few-layered MoS2 domains were transferred to different substrates using a high yield process, including a flexible substrate, preserving the quality of the material. Finally, and mechanically exfoliated MoS2 two-terminal photodetector was designed, fabricated, and measured. Demonstrating thus the capability of heterostructure fabrication and the quality of our synthesis and device fabrication process.

Electronic Effects of Aromatic Rings on the Catalytic Activity of Dioxidomolybdenum(VI)–Hydrazone Complexes

Nine dioxidomolybdenum(VI) complexes were synthesized through the reactions of MoO3 with tridentate hydrazone Schiff base ligands obtained from the reactions of aromatic acid hydrazides (3‐hydroxy‐2‐naphthoic acid hydrazide, 4‐pyridinecarboxylic acid hydrazide and 2‐furoic acid hydrazide) and ortho‐hydroxy aldehyde derivatives (5‐iodo‐2‐hydroxybenzaldehyde, 2‐hydroxy‐1‐naphthaldehyde and 2‐hydroxy‐3‐methoxybenzaldehyde). All of the ligands and complexes were characterized by elemental analysis and spectroscopic methods. The structures of seven complexes were further elucidated by single‐crystal X‐ray diffraction analysis, which indicated distorted octahedral geometries at the metal centres. Spectroscopic and X‐ray analyses indicated that the ligands are coordinated to the molybdenum(VI) ions as dianionic ligands owing to the deprotonation of the phenolic OH and amidic NH groups upon complexation. These complexes were used as catalysts for the oxidation of cyclooctene and thioanisole in the presence of hydrogen peroxide as an environmentally friendly oxidant. To achieve the highest catalytic activity, the effects of important parameters such as the solvent, temperature and molar ratio of the oxidant to the substrate were optimized. The results indicate that electron‐withdrawing substituents on the ligands increase the catalytic activities of dioxidomolybdenum(VI) hydrazone complexes.

Stable Mo/HZSM-5 methane dehydroaromatization catalysts optimized for high-temperature calcination-regeneration

Dehydroaromatization of methane is a promising reaction to directly convert methane into aromatics and hydrogen. The main drawback of this reaction is the rapid deactivation of the Mo/HZSM-5 catalyst due to coking. Regeneration at high reaction temperature by air calcination is not possible due to extensive dealumination of the zeolite. We investigated the structural and textural stability of HZSM-5 as a function of the Mo loading in air at high temperature (550–700°C) and demonstrated that lowering the Mo loading below 2wt% greatly improves the oxidative stability of Mo/HZSM-5. At low Mo loading (1–2wt% Mo), Mo is predominantly in the zeolite micropores as cationic mono- and dinuclear Mo-oxo complexes irrespective of the calcination temperature. At higher loading, most of the initially aggregated Mo-oxide at the external surface is dispersed into the micropores upon calcination above 550°C, resulting in reaction of mobile MoO3 species with framework Al, aluminum molybdate formation and irreversible damage to the zeolite framework. A DFT-based free energy analysis indicates that water formation from reaction of MoO3 with Brønsted acid sites and high concentration of Mo during MoO3 migration causes aluminum molybdate formation. The high oxidative stability of Mo/HZSM-5 with low Mo loading makes them suitable candidates for a novel isothermal (700°C) reaction – air regeneration protocol of methane dehydroaromatization. Whereas a 5wt% Mo/HZSM-5 rapidly lost its initial activity, an optimized 2wt% Mo/HZSM-5 catalyst retained more than 50% of its initial activity after 100 reaction-regeneration cycles (1week) with a substantially improved total aromatics yield.

Synthesis, crystal structure and characterization a new ionic complex MoO2Cl3(MeOH)·H3tptz·Cl2 (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) as epoxidation catalyst

[MoO2Cl3(MeOH)]·H3tptz·Cl2 (1) (where tptz is 2,4,6-tris(2-pyridyl)-1,3,5-triazine) was prepared via reaction of MoO3 with tptz in a stoichiometric ratio of 1:1 in concentrated HCl at room temperature. It was characterized, by means of elemental analysis, FTIR, UV–Vis, 1H NMR and single-crystal X-ray diffraction. The asymmetric unit of the molybdenum(VI) salt 1 contains a 2,2′,2″-(1,3,5-triazine-2,4,6-triyl)tripyridinium cation, a cis-dioxotrichloridomethanolmolybdenum(VI) monoanion and two chloride anions to achieve electrical neutrality. The oppositely charged components in the structure of 1 are bound together by an intricate system of weak N(O)–H⋯Cl hydrogen bonds. The interactions between hydrogen bond donor and acceptor giving rise to three dimensional networks. It was also found that compound 1 successfully catalyzes the epoxidation of various alkenes such as cycoloctene, cyclohexene, norbornene, styrene, α-methyl styrene and trans-stilbene with 30–100% conversion and 80–100% selectivity using tert-butyl hydroperoxide (TBHP) as oxidant. The catalyst can be easily recovered from the reaction mixture and reused at least for three times without significant loss of activity. The superior antibacterial activity of 1 against Bacillus subtilis is also described in this presentation.

Catalytic oxidation of internal and terminal alkenes by oxidoperoxidomolybdenum(VI) and dioxidomolybdenum(VI) complexes

Reaction of oxidoperoxidomolybdenum(VI) species, generated in situ by the reaction of MoO3 in the presence of H2O2, with three Schiff bases H2hap-inh (I), H2hap-nah (II) and H2hap-bhz (III), (derived from the condensation of 2-hydroxyacetophenone with isonicotinoylhydrazide, nicotinoylhydrazide and benzoylhydrazide) results in the formation of oxidoperoxidomolybdenum(VI) complexes, [MoO(O2)(hap-inh)(MeOH)] (1), [MoO(O2)(hap-nah)(MeOH)] (2) and [MoO(O2)(hap-bhz)(MeOH)] (3), respectively. Their dioxidomolybdenum(VI) analogues [MoO2(hap-inh)]n (4) [MoO2(hap-nah)(MeOH)] (5) and [MoO2(hap-bhz)(MeOH)] (6) have also been prepared by reacting equimolar ratio of [MoO2(acac)2] and corresponding ligands. These complexes have been characterized in the solid state as well as in solution namely by spectroscopic techniques (IR, electronic, 1H and 13C NMR), elemental and thermogravimetric analysis. Structures of complexes 3, 4, and 6a ([MoO2(hap-bhz)(DMSO)]) have been confirmed by single crystal X-ray study which reveals that ligands behave as a dibasic tridentate coordinating through ONO functionalities. Sodium bicarbonate assisted oxidation of styrene and cyclohexene using 30% H2O2 as oxidant has been carried out using these catalysts. Under the optimized reaction conditions styrene gave mainly styrene oxide and minor amount of phenylacetaldehyde. Oxidation of cyclohexene gave cyclohexene epoxide selectively. The corresponding dioxidomolybdenum(VI) complexes have relatively lower catalytic activities.

Hierarchical Nanosheet‐Based MoS2 Nanotubes Fabricated by an Anion‐Exchange Reaction of MoO3–Amine Hybrid Nanowires

Moving onward and outward: MoO3–ethylenediamine (EDA) inorganic–organic hybrid nanowires were successfully transformed into hierarchical nanosheet-based MoS2 nanotubes (HNN-MoS2) by anion exchange with S2− anions at elevated temperature (see picture). The resulting nanotubes were highly active catalysts for photoelectrochemical hydrogen evolution by water splitting.

Hierarchical Nanosheet‐Based MoS2 Nanotubes Fabricated by an Anion‐Exchange Reaction of MoO3–Amine Hybrid Nanowires

Wasserstoff aus der Tube: Organisch-anorganische MoO3-Ethylendiamin(EDA)-Hybridnanodrähte wurden durch Anionenaustausch mit S2−-Ionen bei erhöhten Temperaturen in hierarchische nanoschichtbasierte MoS2-Nanoröhren (HNN-MoS2) umgewandelt. Die Nanoröhren sind hoch aktive Katalysatoren für die photoelektrochemische Wasserstoffentwicklung durch Wasserspaltung. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Hydrothermal Synthesis, Crystal Structure, and Catalytic Potential of a One-Dimensional Molybdenum Oxide/Bipyridinedicarboxylate Hybrid

The reaction of MoO3, 2,2'-bipyridine-5,5-dicarboxylic acid (H2bpdc), water, and dimethylformamide in the mole ratio 1:1:1730:130 at 150 °C for 3 days in a rotating Teflon-lined digestion bomb leads to the isolation of the molybdenum oxide/bipyridinedicarboxylate hybrid material (DMA)[MoO3(Hbpdc)]·nH2O (1) (DMA = dimethylammonium). Compound 1 was characterized by scanning electron microscopy, FT-IR and (13)C{(1)H} CP MAS NMR spectroscopies, and elemental and thermogravimetric analyses. The solid state structure of 1 was solved and refined through Rietveld analysis of high resolution synchrotron X-ray powder diffraction data in conjunction with information derived from the above techniques. The material, crystallizing in the noncentrosymmetric monoclinic space group Pc, is composed of an anionic one-dimensional organic-inorganic hybrid polymer, ∞(1)[MoO3(Hbpdc)](-), formed by corner-sharing distorted {MoO4N2} octahedra, which cocrystallizes with charge-balancing DMA(+) cations and one water molecule per metal center. In the crystal structure of 1, the close packing of individual anionic polymers, DMA(+) cations, and water molecules is mediated by a series of supramolecular contacts, namely strong (O-H···O, N(+)-H···O(-)) and weak (C-H···O) hydrogen bonding interactions, and π-π contacts involving adjacent coordinated Hbpdc(-) ligands. The catalytic potential of 1 was investigated in the epoxidation reactions of the bioderived olefins methyl oleate (Ole) and DL-limonene (Lim) using tert-butylhydroperoxide (TBHP) as the oxygen donor and 1,2-dichloroethane (DCE) or (trifluoromethyl)benzene (BTF) as cosolvent, at 55 or 75 °C. Under these conditions, 1 acts as a source of active soluble species, leading to epoxide yields of up to 98% for methyl 9,10-epoxystearate (BTF, 75 °C, 100% conversion of Ole) and 89% for 1,2-epoxy-p-menth-8-ene (DCE, 55 °C, 95% conversion of Lim). Catalytic systems employing the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as solvent could be effectively recycled.

An Octanuclear Molybdenum(VI) Complex Containing Coordinatively Bound 4,4′-di-tert-Butyl-2,2′-Bipyridine, [Mo8O22(OH)4(di-tBu-bipy)4]: Synthesis, Structure, and Catalytic Epoxidation of Bio-Derived Olefins

The reaction of [MoO(2)Cl(2)(di-tBu-bipy)] (1) (di-tBu-bipy = 4,4'-di-tert-butyl-2,2'-bipyridine) with water at 100-120 °C in a Teflon-lined stainless steel autoclave, in an open reflux system, or in a microwave synthesis system gave the octanuclear complex [Mo(8)O(22)(OH)(4)(di-tBu-bipy)(4)] (2) as a microcrystalline powder in good yields. Single crystals of 2 suitable for X-ray diffraction were obtained by the reaction of MoO(3) and di-tBu-bipy in water at 160 °C for 3 days. The molecular structure of 2 comprises a purely inorganic core, Mo(4)O(8)(μ(3)-OH)(2)(μ(2)-O)(2), attached to two peripheral oxo-bridged binuclear units, Mo(2)O(4)(μ(2)-O)(2)(OH)(di-tBu-bipy)(2). The inorganic core is composed of a unique assembly of four {MoO(5)} distorted square pyramids connected to each other via edge-sharing. Overall, the octanuclear complex adopts a highly distorted form strongly resembling an "S"-shaped molecular unit. Complex 2 was applied in the catalytic epoxidation of the biorenewable olefins DL-limonene (Lim) and methyl oleate (Ole), using tert-butylhydroperoxide (TBHP) as an oxygen donor, under mild reaction conditions (55 °C, air). The reactions of Lim and Ole gave the respective epoxide monomers in fairly high selectivities at high conversions (89% 1,2-epoxy-p-menth-8-ene selectivity at 96% Lim conversion; 99% methyl 9,10-epoxystearate selectivity at 94% Ole conversion, reached within 24 h reaction). Iodometric titrations revealed no measurable "non-productive" decomposition of TBHP.

Methanesulfonates of High‐Valent Metals: Syntheses and Structural Features of MoO2(CH3SO3)2, UO2(CH3SO3)2, ReO3(CH3SO3), VO(CH3SO3)2, and V2O3(CH3SO3)4 and Their Thermal Decomposition under N2 and O2 Atmosphere

Oxide methanesulfonates of Mo, U, Re, and V have been prepared by reaction of MoO(3), UO(2)(CH(3)COO)(2)·2H(2)O, Re(2)O(7)(H(2)O)(2), and V(2)O(5) with CH(3)SO(3)H or mixtures thereof with its anhydride. These compounds are the first examples of solvent-free oxide methanesulfonates of these elements. MoO(2)(CH(3)SO(3))(2) (Pbca, a=1487.05(4), b=752.55(2), c=1549.61(5) pm, V=1.73414(9) nm(3), Z=8) contains [MoO(2)] moieties connected by [CH(3)SO(3)] ions to form layers parallel to (100). UO(2)(CH(3)SO(3))(2) (P2(1)/c, a=1320.4(1), b=1014.41(6), c=1533.7(1) pm, β=112.80(1)°, V=1.8937(3) nm(3), Z=8) consists of linear UO(2)(2+) ions coordinated by five [CH(3)SO(3)] ions, forming a layer structure. VO(CH(3)SO(3))(2) (P2(1)/c, a=1136.5(1), b=869.87(7), c=915.5(1) pm, β=113.66(1)°, V=0.8290(2) nm(3), Z=4) contains [VO] units connected by methanesulfonate anions to form corrugated layers parallel to (100). In ReO(3)(CH(3)SO(3)) (P1, a=574.0(1), b=1279.6(3), c=1641.9(3) pm, α=102.08(2), β=96.11(2), γ=99.04(2)°, V=1.1523(4) nm(3), Z=8) a chain structure exhibiting infinite O-[ReO(2)]-O-[ReO(2)]-O chains is formed. Each [ReO(2)]-O-[ReO(2)] unit is coordinated by two bidentate [CH(3)SO(3)] ions. V(2)O(3)(CH(3)SO(3))(4) (I2/a, a=1645.2(3), b=583.1(1), c=1670.2(3) pm, β=102.58(3), V=1.5637(5) pm(3), Z=4) adopts a chain structure, too, but contains discrete [VO]-O-[VO] moieties, each coordinated by two bidentate [CH(3)SO(3)] ligands. Additional methanesulfonate ions connect the [V(2)O(3)] groups along [001]. Thermal decomposition of the compounds was monitored under N(2) and O(2) atmosphere by thermogravimetric/differential thermal analysis and XRD measurements. Under N(2) the decomposition proceeds with reduction of the metal leading to the oxides MoO(2), U(3)O(7), V(4)O(7), and VO(2); for MoO(2)(CH(3)SO(3))(2), a small amount of MoS(2) is formed. If the thermal decomposition is carried out in a atmosphere of O(2) the oxides MoO(3) and V(2)O(5) are formed.

“Hexagonal Molybdenum Trioxide”—Known for 100 Years and Still a Fount of New Discoveries

In 1906, the preparation of “molybdic acid hydrate” was published by Arthur Rosenheim. Over the past 40 years, a multitude of isostructural compounds, which exist within a wide phase range of the system MoO3−NH3−H2O, have been published. The reported molecular formulas of “hexagonal molybdenum oxide” varied from MoO3 to MoO3·0.33NH3 to MoO3·nH2O (0.09 ≤ n ≤ 0.69) to MoO3·mNH3·nH2O (0.09 ≤ m ≤ 0.20; 0.18 ≤ n ≤ 0.60). Samples, prepared by the acidification route were investigated using thermal analysis coupled online to a mass spectrometer for evolved gas analysis, X-ray powder diffraction, Fourier transform infrared, Raman, magic-angle-spinning 1H- and 15N NMR spectroscopy, and incoherent inelastic neutron scattering. A comprehensive characterization of these samples will lead to a better understanding of their structure and physical properties as well as uncover the underlying relationship between the various compositions. The synthesized polymeric parent samples can be represented by the structural formula (NH4)(x∞)(3)[Mo(y square 1−y)O(3y)(OH)(x)(H2O)(m−n)]·nH2O with 0.10 ≤ x ≤ 0.14, 0.84 ≤ y ≤ 0.88, and m + n ≥ 3 − x − 3y. The X-ray study of a selected monocrystal confirmed the presence of the well-known 3D framework of edge- and corner-sharing MoO6 octahedra. The colorless monocrystal crystallizes in the hexagonal system with space group P6(3)/m, Z = 6, and unit cell parameters of a = 10.527(1) Å, c = 3.7245(7) Å, V = 357.44(8) Å3, and ρ = 3.73 g·cm(−3). The structure of the prepared monocrystal can best be described by the structural formula (NH4)(0.13∞)(3)[Mo(0.86 square 0.14)O2.58(OH)0.13(H2O)(0.29−n)]·nH2O, which is consistent with the existence of one vacancy (square) for six molybdenum sites. The sample MoO3·0.326NH3·0.343H2O, prepared by the ammoniation of a partially dehydrated MoO3·0.170NH3·0.153H2O with dry gaseous ammonia, accommodates NH3 in the hexagonal tunnels, in addition to [NH4]+ cations and H2O. The “chimie douce” reaction of MoO3·0.155NH3·0.440H2O with a 1:1 mixture of NO/NO2 at 100 °C resulted in the synthesis of MoO3·0.539H2O. This material is of great interest as a host of various molecules and cations.

Production of CO-Free H2 by Formic Acid Decomposition over Mo2C/Carbon Catalysts

The vapor phase decomposition of formic acid was studied over supported Mo2C catalysts in a flow system. Mo2C deposited on silica is an effective catalyst for both the dehydrogenation of formic acid to yield H2 and CO2, and its dehydration to yield H2O and CO. The extent of the decomposition approached 100% at 623 K. Preparation of the Mo2C catalyst by the reaction of MoO3 with a multiwall carbon nanotube and carbon Norit, however, dramatically altered the product distribution. Dehydrogenation became the dominant process. In optimum case, the selectivity for H2, expressed in terms of the ratio CO2/CO + CO2, was 98–99%, even on total conversion at 423–473 K. The addition of water to the formic acid completely eliminated CO formation and furnished CO-free H2 on Mo2C/carbon catalysts at 373–473 K. Another feature of the Mo2C catalyst is its high stability. No changes in activity or selectivity were observed within 10 h. XP spectra of MoO3 in the course of the formation of 1%Mo2C on carbon Norit in the flow of H2 at different temperatures.

Crystallization of amorphous Si thin films by the reaction of MoO 3/Al nanoengineered thermite

In this work, we investigated a new crystallization method for amorphous silicon (a-Si) using a mixture of nano-energetic materials: molybdenum oxide and aluminum (MoO 3/Al). The purpose of using nano-energetic materials is to improve the performance of a-Si films with a self-propagating exothermic reaction over a period of microseconds without any substrate damage. The mixture of MoO 3/Al nanopowders was used for a thermite reaction for crystallization of a-Si thin films. Characterization results showed that a-Si thin films were successfully crystallized to poly-Si as evidenced by a Raman peak near 519 cm − 1 . The crystalline volume fraction of poly-Si after the nanoengineered thermite reaction was about 94.7% and poly-Si grains was uniformly distributed with an average grain size of around 40–50 nm. These results indicate that high quality poly-Si thin films were successfully prepared on the substrate.