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The catalytic activities of the dispersed NixW(1−x)S2 catalysts were investigated for hydrocracking (HCK) of vacuum residue (VR) at 693 K, 9.5 MPa H2 with the same amount of catalyst loading of 0.113 mmol as a metal basis. The catalysts were prepared in situ in the reaction using nickel acetylacetonate and tungsten hexacarbonyl as Ni and W precursors, respectively. Structural properties of the dispersed catalysts were characterized by extended X-ray absorption fine structure and transmission electron microscopy, which confirmed the formation of a well-dispersed NixW(1−x)S2 phase in the size range 8–10 nm. Moreover, it was demonstrated that the bimetallic metal sulfides of NixW(1−x)S2 feature promotional activity in the VR HCK, showing higher turnover frequency values and less coke formation in VR HCK than monometal sulfides.

Syntheses of transition-metal dichalcogenides (TMDs) using colloidal-chemistry approaches are gaining significant interest in recent years, as these methods enable the morphology and properties of the nanocrystals to be tuned for targeted applications. In this work, by only varying the ligand used during synthesis, we synthesized nanoflowers with oleic acid (OA) and 1T' phase dominated WSe2 nanosheets with oleylamine (OLA). WSe2 nanocrystals show slower rate of formation for the metastable 1T' phase. Surface chemistry analyses of the synthesized nanocrystals by solution NMR establish that neither of the ligands bind strongly to the surface of nanocrystals but are in a dynamic coordination with the WSe2 surface. A further examination of the coordination of tungsten hexacarbonyl (W(CO)(6)) with the respective ligands confirms that W(CO)(6) decomposes in OA, losing its octahedral symmetry, which leads to fast reactivity in the flask. In contrast to this, W(CO)(6) reacts with OLA to form a new complex, which leads to slower reactivity and crystallization of the synthesized nanocrystals in the octahedral 1T' phase. These insights into the influence of precursor-ligand chemistry on reaction outcome and the peculiar surface chemistry of colloidal TMD nanocrystals will be instrumental in developing future colloidal TMD nanocrystals.

Using a metalorganic chemical vapor deposition (MOCVD) technique and a tungsten hexacarbonyl W(CO)6 as a precursor, a stable and continuous coating consisting of nonstoichiometric WC1-x nanoparticles with sizes from 10 to 30 nm on the surface of multi-walled carbon nanotubes (CNTs) was obtained. The resulting hybrid WC1-x/CNTs structures had a developed surface morphology, which contributed to a more complete realization of the potential of the physical and mechanical properties of CNTs when used as reinforcement in composite materials. Comparative assessment of aluminum matrix nanocomposites AA5049 + 5 wt% CNTs and AA5049 + 5 wt% WC1-x/CNTs obtained by high energy ball milling and subsequent hot consolidation at 450°С shows that the WC1-x ceramic coating on the carbon nanotubes surface acts as a barrier layer at the interface, preventing the Al4C3 in situ formation at the matrix/CNT boundary. Coating of carbon nanotubes with WC1-x nanoparticles leads to a significant increase in the physical and mechanical properties of aluminum matrix nanocomposites, in particular, to an increase in the compressive strength from 810 ± 8 MPa to 893 ± 7 MPa, fracture deformation from 3.7% to 4.9%, Young's modulus from 102 ± 6 GPa to 110 ± 4 GPa, and microhardness from 152 ± 6 HV to 176 ± 8 HV in comparison with using of CNTs in the as-synthesized state.

The volatile synthetic products of photochemical vapor generation (PVG) of Os(IV) and W(VI) have been confirmed by GC-MS. Osmium tetroxide has been identified as the species generated from an oxidizing medium of dilute nitric acid, and tungsten hexacarbonyl is produced during PVG from a reducing medium of formic acid. Attempts to ascertain the PVG products of Os and Ru generated in high yield from reducing media (i.e., acetic and formic acids, respectively in the presence of metal sensitizers) were unsuccessful, possibly due to their instability or reactivity with the GC support, and thus remain to be identified using more direct approaches such as Direct Analysis in Real Time (DART)-MS. The mass spectra for OsO₄ and W(CO)₆, reported here for the first time, serve to aid the further development/refinement of mechanistic models for PVG.

This paper studied the feasibility of a new solution-processed method to manufacture black tungsten nanostructures by laser conversion of tungsten hexacarbonyl precursor on the Inconel 625 substrate under argon atmosphere at ambient pressure. The results show that sublimation of the precursor can be prevented if the decomposition temperature (&gt, 170 °C) is achieved using the laser heating method. Three different laser powers from 60–400 W were used to investigate the role of laser parameters on the conversion. It was found that lower laser power of 60 W resulted in a mixture of unconverted precursor and converted tungsten. Higher laser powers &gt, 200 W resulted in α-W (BCC) in one step without further heat treatment. Different oxygen concentrations from 0.5 ppm to 21 vol% were used in the laser canister to investigate the effect of oxygen concentration on the conversion. It was found that the hard vacuum (&gt, 10−4 torr) or hydrogen is not necessary to obtain α-W (BCC). The solar absorptance varied from 63–97%, depending on the amount of precursor deposited on the substrate and oxygen content in the laser canister. This solution-based laser conversion of tungsten precursor is a scalable method to manufacture tungsten coatings for high-temperature applications.

UV photodissociation of tungsten hexacarbonyl W(CO)6 has been studied in the molecular beam conditions using time-of-flight mass spectrometry and velocity map imaging. Irradiation of W(CO)6 by puls...

Electrochemically active nanocrystalline tungsten oxide was synthesized in supercritical carbon dioxide from tungsten hexacarbonyl at 150 °C and 400 bar in the presence of oxygen (partial pressure of 15 bar). The supercritical fluid is a solvent for the precursor (i.e., this is a sc solvothermal synthesis route), whereas the admixed gaseous oxygen serves as an oxidizer, promoting thermal decomposition of the precursor. During the substrate-free synthesis, 200–500 nm aggregates are formed. They consist of smaller grains having the size of about 100 nm. Therefore, a certain structural hierarchy is detected. The electrochemical activity of the as-synthesized particulate material is pronouncedly increasing during both potential cycling and exposure in an aqueous aerated electrolyte. After such a hydration/oxidation process, the electrochemical response of the material shows rather fast and reversible recharging of the entire tungsten-containing phase. This is an indication of facilitated proton transport in bulk of the tungsten oxide phase synthesized in the supercritical carbon dioxide with subsequent hydration/oxidation. Quite differently, the material synthesized at the same temperature only in compressed oxygen (partial pressure of 15 bar) without any presence of supercritical carbon dioxide is highly crystalline one. It does not demonstrate any significant electrochemical rechargeability; neither is the response improving with hydration/oxidation.

We report nanostructured tungsten oxide (WO) cauliflowers for the first time that are fabricated onto silica glass substrate at 400 °C by aerosol assisted chemical vapor deposition using tungsten hexacarbonyl and multiwalled CNTs in toluene. The deposited films are characterized by Scanning electron microscopy, Energy dispersive x-ray spectroscopy, X-ray diffractometry, Fourier transform infrared and UV–VIS spectroscopy and four-point probe for microstructural, optical and electrical properties. Surface morphology exhibits the growth of nanocauliflowers followed by the aggregation of spherical nanoparticles with high angle grain boundaries. Structural information reveals the transformation of triclinic to tetragonal phase with preferential switching from (0 2 0) to (0 0 1) plane having signatures of W-O-W symmetric vibration between (700cm -1 and 900 cm −1 , somewhat perturbed by the addition of doping. In additions, films show inconsistent variation in electrical resistivity (15–10 9 ) Ω-cm due to agglomeration of MWCNTs at grain boundaries and appearance of “nanocracks” due to ionic radii mismatch of tungsten and CNTs at higher doping ratios. Black color films present decrease in optical transmittance for range of 300–400 nm attributed to trapping sites and defects generated due to incorporation of multiwalled CNTs. The splitting of Fermi level as a result of incorporation of MWCNTs caused the increase of band gap energy in range of 3.18 eV, useful in tungsten oxide based new material system which can act as the light harvesting material and energy storage simultaneously.

The 2D transition metal dichalcogenide (TMDC) tungsten disulfide (WS2) has attracted great interest due to its unique properties and prospects for future (opto)electronics. However, compared to molybdenum disulfide (MoS2), the development of a reproducible and scalable deposition process for 2D WS2 has not advanced very far yet. Here, we report on the systematic investigation of 2D WS2 growth on hydrogen (H2)-desorbed sapphire (0001) substrates using a hydrogen sulfide (H2S)-free metal-organic vapor phase epitaxy (MOVPE) process in a commercial AIXTRON planetary hot-wall reactor in 10 × 2” configuration. Tungsten hexacarbonyl (WCO, 99.9 %) and di-tert-butyl sulfide (DTBS, 99.9999 %) were used as MO sources, nitrogen (N2) was selected as carrier gas for the deposition processes (standard growth time 10 h). In an initial study, the impact of growth temperature on nucleation and growth was investigated and an optimal value of 820 °C was found. The influence of the WCO flow on lateral growth was investigated. The aim was to maximize the edge length of triangular crystals as well as the total surface coverage. Extending gradually the growth time up to 20 h at optimized WCO flow conditions yields fully coalesced WS2 samples without parasitic carbon-related Raman peaks and with only sparse bilayer nucleation. After substrate removal, a fully coalesced WS2 film was implemented into a light-emitting device showing intense red electroluminescence (EL).

Tungsten- and nickel-containing coatings have been produced on the surface of synthetic diamond crystals by rotary chemical vapor deposition (RCVD) using tungsten hexacarbonyl, W(CO)6, and nickelocene, Ni(C5H5)2, as gaseous precursors. The thickness, composition, and morphology of the coatings have been shown to depend on the RCVD process duration and reactant concentrations in the vapor phase. The synthetic diamond microcrystals with tungsten- and nickel-containing coatings have been used to produce copper–diamond heat-conducting composites. Powder mixtures containing 50 vol % diamond with a particle size of 50, 100, or 200 μm have been consolidated by spark plasma sintering or hot pressing. It has been shown that the highest relative density (97%) and thermal conductivity (340 W/(m K)) are offered by the composites produced by spark plasma sintering using tungsten carbide-coated 50-μm diamond crystals.

A phenanthroline-based ligand L1 ((((1,10-phenanthrolin-5-yl)imino)methyl)-6-methoxyphenol) was synthesized and reacted with chromium, molybdenum, and tungsten hexacarbonyl to form ultraviolet (UV) activable photoCORMs C1, M1, and T1, respectively. All compounds were characterized via IR, 1H-NMR, 13C-NMR, and CHN elemental analyses, and the X-ray crystal structures of L1 and M1 were determined. The half-life of the photoCORMs decreased with an increasing concentration and the rate of CO release increased in the order of T1

Reduction of tungsten hexacarbonyl by the divalent samarium(II) complex [Sm2 (N4 Et8 )(thf)4 ] ((N4 Et8 )4- =meso-octaethylcalix[4]pyrrolide) in toluene at ambient temperature gave the remarkable heteronuclear mixed-valent samarium(II/III)/tungsten complex [{(thf)2 SmII (N4 Et8 )SmIII (thf)}2 {(μ-OC)2 W2 (CO)8 }], which features the trapping of a rare [W2 (CO)10 ]2- anion with an unsupported W-W bond.

Selective bond cleavage via vibrational excitation is the key to active control over molecular reactions. Despite its great potential, the practical implementation in condensed phases have been hampered to date by poor excitation efficiency due to fast vibrational relaxation. Here we demonstrate vibrationally mediated, condensed-phase molecular dissociation by employing intense plasmonic near-fields of temporally-shaped mid-infrared (mid-IR) pulses. Both down-chirping and substantial field enhancement contribute to efficient ladder climbing of the carbonyl stretch vibration of W(CO)6 in n-hexane solution and to the resulting CO dissociation. We observe an absorption band emerging with laser irradiation at the excitation beam area, which indicates that the dissociation is followed by adsorption onto metal surfaces. This successful demonstration proves that the combination of ultrafast optics and nano-plasmonics in the mid-IR range is useful for mode-selective vibrational ladder climbing, paving the way toward controlled ground-state chemistry., There is a growing interest in controlling the chemical process at molecular level. Here the authors show the mid-IR chirped pulse driven ground-state dissociation of condensed phase tungsten hexacarbonyl using efficient vibrational ladder climbing process by employing plasmonic near-field enhancement.

Complexes with weakly coordinating ligands are often formed in chemical reactions and can play key roles in determining the reactivity, particularly in catalytic reactions. Using time-resolved X-ray absorption fine structure (XAFS) spectroscopy in combination with time-resolved IR (TRIR) spectroscopy and tungsten hexacarbonyl, W(CO)6, we are able to structurally characterize the formation of an organometallic alkane complex, determine the W-C distances, and monitor the reactivity with silane to form an organometallic silane complex. Experiments in perfluorosolvents doped with xenon afford initially the corresponding solvated complex, which is sufficiently reactive in the presence of Xe that we can then observe the coordination of Xe to the metal center, providing a unique insight into the metal-xenon bonding. These results offer a step toward elucidating the structure, bonding, and chemical reactivity of transient species by X-ray absorption spectroscopy, which has sensitivity to small structural changes. The XAFS results indicate that the bond lengths of metal-alkane (W-H-C) bond in W(CO)5(heptane) as 3.07 (±0.06) Å, which is longer than the calculated W-C (2.86 Å) for binding of the primary C-H, but shorter than the calculated W-C (3.12 Å) for the secondary C-H. A statistical average of the calculated W-C alkane bond lengths is 3.02 Å, and comparison of this value indicates that the value derived from the XAFS measurements is averaged over coordination of all C-H bonds consistent with alkane chain walking. Photolysis of W(CO)6 in the presence of HSiBu3 allows the conversion of W(CO)5(heptane) to W(CO)5(HSiBu3) with an estimated W-Si distance of 3.20 (±0.03) Å. Time-resolved TRIR and XAFS experiments following photolysis of W(CO)6 in perfluoromethylcyclohexane (PFMCH) allows the characterization of W(CO)5(PFMCH) with a W-F distance of 2.65 (±0.06) Å, and doping PFMCH with Xe allows the characterization of W(CO)5Xe with a W-Xe bond length of 3.10 (±0.02) Å.

Metal–organic complexes are widely used across disciplines for energy and biological applications, however, their photophysical and photochemical reaction coordinates remain unclear in solution due to pertaining molecular motions on ultrafast time scales. In this study, we apply transient absorption and tunable femtosecond stimulated Raman spectroscopy (FSRS) to investigate the UV photolysis of tungsten hexacarbonyl and subsequent solvent binding events. On the macroscopic time scale with UV lamp irradiation, no equilibrated intermediate is observed from W(CO)6 to W(CO)5(solvent), corroborated by vibrational normal mode calculations. Upon 267 nm femtosecond laser irradiation, the excited-state absorption band within ∼400—500 nm exhibits distinct dynamics in methanol, tetrahydrofuran, and acetonitrile on molecular time scales. In methanol, solvation of the nascent pentacarbonyl–solvent complex occurs in ∼8 ps and in tetrahydrofuran, 13 ps which potentially involves the associative oxygen-donating ligand re...

Metalorganic chemical vapor deposition (MOCVD) is a promising technique to form large-area, uniform films of monolayer or few-layer transition metal dichalcogenide (TMD) thin films; however, unintentional carbon incorporation is a concern. In this work, we report the presence of a defective graphene layer that forms simultaneously during MOCVD growth of tungsten diselenide (WSe2) on sapphire at high growth temperature and high Se:W ratio when using tungsten hexacarbonyl (W(CO)6) and dimethyl selenide ((CH3)2Se, DMSe) as precursors. The graphene layer alters the surface energy of the substrate reducing the lateral growth and coalescence of WSe2 domains. The use of hydrogen selenide (H2Se) instead of DMSe eliminates the defective graphene layer enabling coalesced monolayer and few-layer WSe2 films.

Pyrolytic tungsten coatings have been produced on the surface of ash microspheres under steady-state conditions using tungsten hexacarbonyl as a precursor. The nanostructured composites thus obtained were characterized by X-ray diffraction and scanning electron microscopy. We have studied the kinetics of the catalytic reduction of germanium tetrachloride with hydrogen in the temperature range 423–973 K in the presence of the composites as catalysts and determined the reaction order and activation energy for the catalytic reduction of germanium tetrachloride with hydrogen.

Irradiation- and collision-induced fragmentation studies provide information about geometry, electronic properties and interactions between structural units of various molecular systems. Such knowledge brings insights into irradiation-driven chemistry of molecular systems which is exploited in different technological applications. An accurate atomistic-level simulation of irradiation-driven chemistry requires reliable models of molecular fragmentation which can be verified against mass spectrometry experiments. In this work fragmentation of a tungsten hexacarbonyl, W(CO)$_6$, molecule is studied by means of reactive molecular dynamics simulations. The quantitatively correct fragmentation picture including different fragmentation channels is reproduced. We show that distribution of the deposited energy over all degrees of freedom of the parent molecule leads to thermal evaporation of CO groups and the formation of W(CO)$_n^+$ ($n = 0-5$) fragments. Another type of fragments, WC(CO)$_n^+$ ($n = 0-4$), is produced due to cleavage of a C--O bond as a result of the localized energy deposition. Calculated fragment appearance energies are in good agreement with experimental data. These fragmentation mechanisms have a general physical nature and should take place in radiation-induced fragmentation of different molecular and biomolecular systems., Comment: 11 pages, 6 figures, submitted to European Physical Journal D

We observed the bare W2(+) metal cation upon electron ionization of the weakly bound W(CO)6 dimer. This metal cation can be only observed due to the fast conversion of the weak cluster bond into a strong covalent bond between the metal moieties.

International audience; Experiments on chemical vapor deposition of W(CO)6- derived films on silicon substrates were carried out at total pressure of 5-10 Torr within the temperature range of 250-350 oС in Ar or H2 flow. Metallic, carbide and oxide phases composed the obtained films. Deposition in presence of hydrogen results in the increase of the metal content in the film. Sublimed palladium hexafluoracetylacetonate Pd(hfa)2 was used for Pd catalytic promotion of the deposition process. Codeposition with Pd(hfa)2 in hydrogen increases W-metal fraction and oxygen content while the Pd content is up to 10 at.%. Influence of vacuum ultraviolet (VUV) radiation from Xe excimer lamp (λ~172 nm) on the quality of the obtained films was investigated. It was found that VUV irradiation can reduce the oxygen-content in the film while W-metal fraction slightly increases. In all films, oxygen was in the form of WO3 and carbon was mainly incorporated as a graphite metastable phase. The influence of other chemical additives is discussed.

Aerosol assisted chemical vapour deposition (AACVD) is used to deposit tungsten oxide thin films from tungsten hexacarbonyl (W(CO)6) at 339 to 358 °C on quartz substrate. The morphologies of as-deposited thin films, which are comprised of two phases (W25O73 and W17O47), vary from planar to nanorod (NR) structures as the distance from the inlet towards the outlet of the reactor is traversed. This is related to variation of the actual temperature on the substrate surface (ΔT = 19 °C), which result in a change in growth mode due to competition between growth rate (perpendicular to substrate) and nucleation rate (parallel to substrate). When the ratio of perpendicular growth rate to growth rate contributed by nucleation is higher than 7.1, the as-deposited tungsten oxide thin film forms as NR. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Phospholipid bilayers are frequently used as models for cell membranes. Here the influence of cholesterol on the structural dynamics in the interior of 1,2-dilauroyl-sn-glycero-3-phosphocholine (dilauroylphosphatidylcholine, DLPC) vesicles and DLPC planar bilayers are investigated as a function of cholesterol concentration. 2D IR vibrational echo spectroscopy was performed on the antisymmetric CO stretch of the vibrational probe molecule tungsten hexacarbonyl, which is located in the interior alkyl regions of the bilayers. The 2D IR experiments measure spectral diffusion, which is caused by the structural fluctuations of the bilayers. The 2D IR measurements show that the bilayer interior alkyl region dynamics occur on time scales ranging from a few picoseconds to many tens of picoseconds. These are the time scales of the bilayers' structural dynamics, which act as the dynamic solvent bath for chemical processes of membrane biomolecules. The results suggest that at least a significant fraction of the dynamics arise from density fluctuations. Samples are studied in which the cholesterol concentration is varied from 0% to 40% in both the vesicles (72 nm diameter) and fully hydrated planar bilayers in the form of aligned multibilayers. At all cholesterol concentrations, the structural dynamics are faster in the curved vesicle bilayers than in the planar bilayers. As the cholesterol concentration is increased, at a certain concentration there is a sudden change in the dynamics, that is, the dynamics abruptly slow down. However, this change occurs at a lower concentration in the vesicles (between 10% and 15% cholesterol) than in the planar bilayers (between 25% and 30% cholesterol). The sudden change in the dynamics, in addition to other IR observables, indicates a structural transition. However, the results show that the cholesterol concentration at which the transition occurs is influenced by the curvature of the bilayers.

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Tungsten oxide is deposited by atomic layer deposition (ALD) using tungsten hexacarbonyl [W(CO)6] and ozone [O3]. Growth characteristic is studied in detail by in-situ quartz crystal microbalance (QCM). A narrow temperature window is observed with a saturated growth rate of 0.21 A per ALD cycle. In-situ Fourier transform infrared (FTIR) vibration spectroscopy investigation is performed to determine the surface chemistry during each ALD half cycle under linear growth regime. X-ray photo electron spectroscopy confirms the deposit presence and chemical nature of tungsten and oxygen in the as-deposited WO3 film. The as deposited films are found amorphous which crystalized to monoclinic WO3 upon annealing.

Vibrational dynamics of the T1u CO stretching mode of tungsten hexacarbonyl is explored when the molecule is embedded in a nitrogen matrix at low temperature. Experiments combined infrared (IR) absorption spectroscopy and IR stimulated photon echoes at the femtosecond time scale. W(CO)6 is found to be trapped in two main families of sites differing by their symmetry (called hereafter Oh and D2h sites). In Oh sites, the vibrational coherence is strongly temperature dependent, exhibiting a coupling with librational phonons of the nitrogen lattice. Perturbation in D2h sites results in the splitting of the T1u band in three components. Each component is inhomogeneously broadened, with dephasing times in the tens of picoseconds, and is weakly coupled to the lattice phonons. Experiments in solid krypton are performed to compare the effect of atomic and diatomic host lattices. Dephasing time in Kr does not depend on temperature and remains in the hundreds of picoseconds, highlighting the molecular origin of the dephasing process in N2. Additionally, nonlinear signals show oscillations due to quantum beats and polarization interferences between different frequency components of the induced third order polarization, giving information, in particular, on the overtone vibrational transition.

Thin films of transition metals oxides are studied and comparison is made for two types of mixed precursors, first containing only hexacarbonyls, and second containing tungsten hexacarbonyl and vanadyl acetylacetonate (Vanadium (III) acetylacetonate). The best electrochromic material is WO3, although when deposited by Atmospheric Pressure Chemical Vapour Deposition (APCVD) films of WO3 grow very slowly. In production stage, the growth-rate is very important factor for assuring a flow-through process. Our previous investigations showed that addition of a small fraction of lower temperature precursor such as Mo(CO)6, or V(CO)6, to the basic precursor of W(CO)6 result in higher growth rate of films. Our recent studies on mixed WxV1-xO3 showed excellent substrate coverage and high growth-rate. V(CO)6 is a lower thermally stable precursor that allows the first nuclei-islands to be formed on the hot substrates which further facilitate the tungsten oxide film deposition. However V(CO)6 is much too expensive for large-scale production, thus we adopted another compound as precursor - vanadium acetylacetonate, expecting eventual growth-rate increase. The paper describes optical properties of films of vanadium oxide grown in result of utilizing the acetylacetonate. Besides, the paper describes our attempt to deposit mixed films of tungsten/vanadium using a mixed precursor of vanadyl acetylacetonate and tungsten hexacarbonyl. To our knowledge this is a new mixed precursor based on largely used single precursors namely W(CO)6 and Vanadium acetylacetonate. Efforts were needed to adjust the mixed precursor ratio, keeping in mind the vapour pressures of the two chemicals at the deposition temperatures used. The paper presents the results for the visible transmittance and the film material modulation properties, studied by FTIR and Raman spectra. The dependence of the films optical behavior on APCVD process parameters, substrate temperatures, vapour source temperature and post deposition annealing is presented.

Electron ionization of neat tungsten hexacarbonyl (W(CO)6) clusters has been investigated in a crossed electron-molecular beam experiment coupled with a mass spectrometer system. The molecule is used for nanofabrication processes through electron beam induced deposition and ion beam induced deposition techniques. Positive ion mass spectra of W(CO)6 clusters formed by electron ionization at 70 eV contain the ion series of the type W(CO)n (+) (0 ≤ n ≤ 6) and W2(CO)n (+) (0 ≤ n ≤ 12). In addition, a series of peaks are observed and have been assigned to WC(CO)n (+) (0 ≤ n ≤ 3) and W2C(CO)n (+) (0 ≤ n ≤ 10). A distinct change of relative fragment ion intensity can be observed for clusters compared to the single molecule. The characteristic fragmentation pattern obtained in the mass spectra can be explained by a sequential decay of the ionized organometallic, which is also supported by the study of the clusters when embedded in helium nanodroplets. In addition, appearance energies for the dissociative ionization channels for singly charged ions have been estimated from experimental ion efficiency curves.

Preparation route of new tungsten-containing TiO2 powders (W-TiO2) and their activity under visible light are reported. The photocatalysts were prepared by the sol–gel method and by grinding anatase powder with a dopant precursor followed by calcinations (surface impregnation method). Tungsten oxide and tungsten hexacarbonyl were used as tungsten sources in both photocatalyst preparation procedure. The obtained photocatalysts were subsequently characterized by a BET method, X-ray photoelectron emission spectroscopy (XPS) and X-ray powder diffraction analysis (XRD). Degradation efficiency of phenol and formation of phenol degradation by-products were compared for two systems: W-doped TiO2 under visible light and P-25 under UV irradiation. The highest photoactivity under visible light was observed for 3%-W-TiO2 and it was three times higher than photoactivity of pure TiO2. Phenol oxidation in the presence of W-TiO2 and visible light leads to formation of hydroxyproduct (catechol) and phenol ring cleavage products (muconic aldehyde).

A study on chemical vapor deposition(CVD) of and the electrochromic properties of the CVD films have been carried out. The crystalinity, purity, and growth rate of the films depending on substrate temperatures are investigated. The highest growth rate is at the substrate temperatures above and the estimated activation energy for overall film growth is about 45.9 kJ/mol at the temperatures of , where the CVD process is controlled by a surface reaction kinetics. The films grown below are amorphous, while those deposited above are crystalline. The effects of thickness and deposition temperature of the films on electrochromic activity are also investigated. The coloration efficiency of the films increases with increase in film thickness and decrease in deposition temperature.

In the present investigation, W 20–40wt.% Cu nanocomposite powders with average sizes ranging between 25 and 30 nm were synthesized by a soft chemical approach using tungsten hexacarbonyl [W(CO) 6 ] and copper acetonyl acetonate [Cu(acac) 2 ] as metal precursors. Particle size, morphology and distribution were measured using transmission electron microscope (TEM) and small angle X-ray scattering (SAXS). Surfactant coating on W Cu composite powders was removed on heat treatment of powders at 450 °C in hydrogen atmosphere for 1 h. Elemental analyses of as-synthesized and annealed (at 450 °C) W Cu nanocomposite powders were carried out using inductively coupled plasma-optical emission spectrometer (ICP-OES) and Leco gas analyzers. X-ray diffraction studies showed that the tungsten phase is amorphous while the crystal structure of copper phase is fcc in as-synthesized W Cu nanocomposite powders. After annealing at 700 °C peaks corresponding to bcc tungsten are observed and peaks corresponding to fcc copper become sharper. Relative densities of 98.2%, 98.8% and 99.2% were achieved for W 20wt.% Cu, W 30wt.% Cu, and W 40wt.% Cu composite powders respectively when sintered at 1000 °C.

UV-irradiation of the diorganosilane [4-tBu-2,6-{P(O)(OiPr)2}2C6H2]SiH2Ph in the presence of W(CO)6 provided a mixture consisting of the diorganosilylene tungsten pentacarbonyl complex [4-tBu-2,6-{P(O)(OiPr)2}2C6H2](Ph)SiW(CO)5 (2), the organosilylium salt [4-tBu-2,6-{P(O)(OiPr)2}2C6H2Si(H)Ph]+[{(CO)5W}2H]– (3), and an unidentified species. UV-irradiation of the triorganosilane [4-tBu-2,6-{P(O)(OiPr)2}2C6H2]SiHPh2 in presence of W(CO)6 provided the organosilylium salt [4-tBu-2,6-{P(O)(OiPr)2}2C6H2SiPh2]+[{(CO)5W}2H]– (6) whereas, under the same conditions, no reaction was observed between the tetraorganosilane [4-tBu-2,6-{P(O)(OiPr)2}2C6H2]SiPh3 and W(CO)6. The reaction of compound 2 with Ph3C+PF6– gave the fluorine-substituted silylene complex [4-tBu-2,6-{P(O)(OiPr)2}2C6H2](F)SiW(CO)5 (4) whereas the reactions of 3 with Ph4PBr and 5 with water gave the benzoxasilaphospholes 3a, 3b, and 7, respectively. The compounds 2 and 6 were isolated and characterized by 1H, 13C, 29Si, 31P NMR, and IR spectroscopy, electrospray ionization mass spectrometry, and in case of 2 also by single-crystal X-ray diffraction analysis. The compounds 3, 3a, 3b, 4, and 7 were not isolated but identified unambiguously by NMR spectroscopy and electrospray ionization mass spectrometry.

Tungsten nanoparticles were prepared by thermal decomposition of tungsten hexacarbonyl [W(CO) 6 ] (2 mmol) at 160 °C in presence of a mixture of (1:1) surfactants, oleic acid (6 mmol) and trioctyl phosphine oxide (TOPO) (6 mmol) under a blanket of Ar gas. The synthesized tungsten nanoparticles without surfactant are flocculated. With increase in concentration of surfactant mixture to 12 mmol each, agglomeration of several tungsten nanoparticles are observed. Characterization of surfactant coated tungsten nanoparticles were carried out using Fourier transform infrared spectroscopy (FTIR). Chemical characterizations of synthesized tungsten nanoparticles were done using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES) and LECO gas analyzers. XPS study shows the W 0 oxidation state of tungsten nanopowders. Structural characterization of synthesized tungsten nanoparticles were conducted by X-ray diffraction (XRD), which shows that the as-synthesized tungsten nanoparticles are amorphous in nature and they become body centered cubic crystalline after annealing. Particle size, shape and distribution were characterized using small-angle X-ray scattering (SAXS), environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM).

Doubly charged tungsten hexacarbonyl W(CO) 6 2+ ions were made to collide with K and Cs targets to give singly and doubly charged positive ions by collision-induced dissociation (CID). The internal energy depositions resulting from the electron transfer were evaluated from the relative abundances of the singly charged fragment W(CO) n + ions. The internal energy deposition resulting from the electron transfer with the Cs target was very narrow and centered at a particular energy, 8.2 eV above the energy level of the charge reduced W(CO) 6 + ion, which was higher than 7.2 eV with the K target. These internal energies correspond to energy differences of 2.9 and 3.5 eV between the entrance channel of W(CO) 6 2+ + Cs (or K) and the exit channel of W(CO) 6 + * + Cs + (or K + ), respectively. The potential energy between W(CO) 6 2+ ions and the alkali metal atoms was found to decrease markedly in the entrance channel of the electron transfer as a result of the large polarizability of the alkali metal targets. The internuclear separation of the Landau–Zener potential crossing of the electron transfer between a W(CO) 6 2+ ion and the Cs target was evaluated as 6.8 × 10 −8 cm, which was larger than the value for the K target (5.9 × 10 −8 cm). Large cross sections for the electron transfer of the order of 10 −14 cm 2 , estimated from the internuclear distances, indicate that the electron capture of the doubly charged ion on collisions with an alkali metal targets is a very effective process for producing charge-reduced ions. The difference in the cross sections between K and Cs target indicates that a target having lower ionization energy is more effective for electron transfer.

Low temperature photoreaction between tungsten hexacarbonyl and ferrocenylacetylene yielded two unusual metal containing stable compounds, the tritungsten cluster, [W3(μ-η2,η2-(H)C≡CFc)2(CO)12](1), and ditungsten-1,4,5,8-ferrocenylcyclodecatetraene, [W2{μ-η2,η2,η2,η2-(Fc)C=C(H)C(H)=C(Fc)C(Fc)=C(H)C(H)=C(Fc)}(CO)6] (2). Both compounds were characterised by IR and 1H and 13C NMR spectroscopy and their molecular structures established by single crystal X-ray diffraction methods., © Elsevier

Crystalline tungsten diselenide (WSe2) nanoparticles have been synthesized by a gas phase reaction using tungsten hexacarbonyl and elemental selenium as precursors. The WSe2 nanoparticle morphology varies from the spherical shape to flake-like layered structures. Mean size in smaller dimension are less than 5 nm and the number of layers decreased linearly with decreasing of reaction time and concentration of carbonyl in the gas phase. The mean value of interlayer distance in direction is comparable with the microscopic values. The selenium-to-tungsten atomic ratios of 2.07, 2.19 and 2.19 were determined respectively, approach to the stoichiometric ratio of 2:1. Main impurities are oxygen and carbon and strongly interrelated with carbonyl concentration in the gas phase.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7356

Tungsten hexacarbonyl was immobilized onto polystyrene (2% cross-linked with divinylbenzene) via different linkages to afford polymer-supported tungsten carbonyl catalysts. These catalysts were used for the epoxidation of cis-cyclooctene with hydrogen peroxide. The effect of different solvents and oxygen donors were investigated in the epoxidation of cis-cyclooctene with catalyst 2e and CH3CN was chosen as reaction media and H2O2 as oxidant. We found that the polymer-supported tungsten carbonyl catalysts were efficient and reusable catalysts in this reaction. These catalysts could be reused 3–10 times in the epoxidation of cis-cyclooctene.