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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.

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.

Flexible electrochromic organo-tungsten-iron oxide (WFexOyCz) films are rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide; PET/ITO) substrates by a low temperature-atmospheric pressure-plasma polymerization method with an atmospheric pressure plasma jet (APPJ) for a short exposed duration of 48 s. The precursor vapors of tungsten hexacarbonyl [W(CO)6] and biscyclopentadienyl iron [ferrocene; Fe(C5H5)2] are mixed with O2 gases at various gas flow rates, injected into air plasma jet and sprayed onto PET/ITO substrates at room temperature (~23 °C) and at atmospheric pressure (1.013 × 105 Pa). Flexible electrochromic WFexOyCz films are synthesized with a specific addition of oxygen gases with superior lithium electrochromic properties as demonstrated by a potential sweep alternating between −1 V and 2 V at a scan rate of 40 mV/s in a 1 M LiClO4-propylene carbonate electrolyte. With amorphous WFexOyCz films produced with an APPJ by adding oxygen gases at a specific flow rate of 0.5 sccm, a high value in oxygen deficiency up to 0.189 allows more Li+ ions to intercalate into and deintercalate out of the film. Significant coloration and bleaching are proven by the high values in optical transmittance modulation (ΔT) of up to 70.3%, optical density (ΔOD) up to 0.77 and color efficiency (η) up to 61.3 cm2/C, at a wavelength of 800 nm, respectively.

We report on a new hybrid heterojunction gas-sensitive device by combining a molecular material with a metal oxide. WO3 was synthesised via an aerosol-assisted chemical vapour deposition technique from a tungsten hexacarbonyl precursor. Onto an inorganic film, LuPc2 was vacuum evaporated. The morphology of the WO3–LuPc2 hybrid films is dominated by the morphological features of the tungsten oxide film, as shown by scanning electron microscopy and atomic force microscopy. Raman spectroscopy of the device confirms the presence of both materials. The non-linear I–V characteristics demonstrate the existence of an energy barrier at the interface between the inorganic and molecular materials. The interfacial phenomenon was confirmed by means of impedance spectroscopy. Finally, the positive response to ammonia confirms the n-type nature of the charge carriers responsible for the transport properties through the device, in accordance with the n-type conductivity of WO3. This response is fully reversible whatever the relative humidity value in the range 10–70% rh. Even though the current is shifted when the relative humidity decreases, ammonia sensitivity remains almost unchanged (2.5 nA ppm−1) for rh ranging from 30 to 50%. It is worth noting that the present device operates at room temperature with excellent reversibility and stability, showing the lowest limit of detection for ammonia ever reported for this device architecture (250 ppb).

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.

An investigation has been taken on enhancing lithium electrochromic performances of mixed organotungsten oxide (WOyCz)/organotitanium oxide (TiOyCz) films, co-synthesized onto 60 Ω/square flexible polyethylene terephthalate (PET)/indium tin oxide (ITO) substrates by a low temperature plasma polymerization method at various mixed concentrations of precursors tungsten hexacarbonyl W(CO)6 and titanium n-butoxide Ti(C4H9O)4. The plasma polymerized-organo‑tungsten‑titanium oxides (WTixOyCz) films possess notable electrochromic performances while switch tested by a potential sweep from −1 V to 1 V at a scan rate of 50 mV/s and from 1 V to −1 V at a scan rate of −50 mV/s for 200 cycles of reversible Li+ ion intercalation and de-intercalation in a 1 M LiClO4-PC electrolyte, still after bended 360o around a 2.5 cm diameter rod for 1000 cycles. Optical modulation (ΔT) of 74.8% for WOyCz films at a wavelength of 850 nm is appreciably progressed of up to 82.7% for WTixOyCz films as co-deposited by a low temperature plasma polymerization method.

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

We report a mild synthetic method to access Sn nanocrystals with tunable diameter and narrow size distribution (6–8%). The self-templated formation of various types of Sn chalcogenide hollow nanostructures including oxides, sulfides, selenides, and tellurides is also demonstrated for the first time. The use of air-stable tungsten hexacarbonyl that produces carbon monoxide at elevated temperature to reduce the SnCl2 precursor and coordinate the nanoparticle surface is thought to play an essential role in this method. This synthesis method is likely to be extended to other metal systems and could find potential applications including battery anodes and catalysts.

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.

Tungsten oxides, including WO3 and mixed valent oxides, are formed in unpolished porous Vycor glass (PVG) by ultraviolet photolytic decomposition of adsorbed tungsten hexacarbonyl. The relative amounts of the oxides formed are determined by a competition between aggregation and oxidation, and both are influenced by CO pressure gradients created by the photoinduced release of CO within the nanoporous silica matrix. These gradients sweep the hexacarbonyl precursor into the outer regions of the PVG, increasing amounts of tungsten nearer the surface, thereby enhancing the rate of aggregation relative to the rate of oxidation and promoting the formation of the mixed valent oxides. Thermolysis of the physisorbed hexacarbonyl, on the other hand, produces predominantly WO3. Thermolysis promotes desorption of the physisorbed W(CO)6, reducing the amount of tungsten available, permitting oxidation to be the predominant process over aggregation, leading to WO3 formation.

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.

We demonstrated humidity sensing characteristics based on a suspended single tungsten nanowire. The nanowire is synthesized on batch-processed microelectrodes by focused ion beam-chemical vapor deposition (FIB-CVD) using tungsten hexacarbonyl [W(CO) 6 ] as the precursor gas. Two different humidity sensing mechanisms, electrothermal sensing and chemical sensing, were demonstrated using as-deposited and annealed nanowires. When the relative humidity level was increased from 30% to 80%, the DC resistance of the as-deposited nanowire immediately showed 5.68% decrease by electrothermal sensing mechanism. Since the as-deposited nanowire is amorphous structure, no chemical sensing response was observed for the as-deposited nanowire case. On the contrary, the tungsten nanowire annealed at 700 °C showed a 13.2% increase in its DC resistance by the chemical sensing mechanism when the relative humidity level was increased from 40% to 80%, revealing enhanced sensor responsiveness and improved linearity than the electrothermal sensing using as-deposited nanowire.

Highly efficient epoxidation of alkenes with H2O2 catalyzed by tungsten hexacarbonyl supported on multi-wall carbon nanotubes (MWCNTs) modified with 1,2-diaminobenzene is reported. The prepared catalyst, [W(CO)6@DAB-MWCNT], was characterized by elemental analysis, scanning electron microscopy, FT-IR, and diffuse reflectance UV-Vis spectroscopic methods. The prepared catalyst was applied as an efficient catalyst for green epoxidation of alkenes with hydrogen peroxide in CH3CN. This heterogeneous metal carbonyl catalyst showed high stability and reusability in epoxidation without loss of its catalytic activity.

Carbon nanotubes (CNTs) were coated by tungsten layer using metal organic chemical vapor deposition process with tungsten hexacarbonyl as a precursor. The W-coated CNTs (W-CNTs) were dispersed into Cu powders by magnetic stirring process and then the mixed powders were consolidated by spark plasma sintering to fabricate W-CNTs/Cu composites. The CNTs/Cu composites were fabricated using the similar processes. The friction coefficient and mass wear loss of W-CNTs/Cu and CNTs/Cu composites were studied. The results showed that the W-CNT content, interfacial bonding situation, and applied load could influence the friction coefficient and wear loss of W-CNTs/Cu composites. When the W-CNT content was 1.0 wt.%, the W-CNTs/Cu composites got the minimum friction coefficient and wear loss, which were decreased by 72.1% and 47.6%, respectively, compared with pure Cu specimen. The friction coefficient and wear loss of W-CNTs/Cu composites were lower than those of CNTs/Cu composites, which was due to that the interfacial bonding at (W-CNTs)-Cu interface was better than that at CNTs-Cu interface. The friction coefficient of composites did not vary obviously with increasing applied load, while the wear loss of composites increased significantly with the increase of applied load.

The preparation, characterization, and catalytic activity of W(CO)6 supported on multi-wall carbon nanotubes modified with 4-aminopyridine is reported. The catalyst, [W(CO)5@Apy-MWCNT], was characterized by physico-chemical and spectroscopic methods and found to be an efficient heterogeneous catalyst for green epoxidation of alkenes with hydrogen peroxide in MeCN solvent. The catalyst showed good stability and reusability properties in the epoxidation reactions.

In this study we have fabricated tungsten containing nano-wires using focused electron and ion beams from a tungsten hexacarbonyl precursor. The temperature dependent conductive properties of the wires have been investigated. Although a superconducting transition (at ∼ 5.5 K) has been observed in ion beam deposited wires, electron beam deposited wires display non-metallic conduction properties consistent with a variable range hopping conduction mechanism. Micro-structural and compositional analysis has been performed using transmission electron microscopy and associated techniques. The observed disorder of the as-deposited wires, together with the higher oxygen and lower metal content of the electron beam deposited wires was found to correlate well with the low temperature electrical properties. In addition, the electron beam deposited wires were shown to be particularly susceptible to irradiation damage when illuminated using 200 kV electrons in the transmission electron microscope. With electron doses in the region of ∼ 50 A/cm2 the as-deposited disordered structure was refined locally to give regions of randomly orientated nano-crystallites.

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

A new method is developed to obtain crystalline nanorods of WO 3 using tungsten organometallic compound, tungsten hexacarbonyl, at a low temperature of around 700°C. The diameters of the nanorods were in the range of 20–50 nm, and their lengths were up to several micrometers. The WO 3 nanorods had a clean surface without any particles. HRTEM and SAED pattern analysis results showed that the synthesized WO 3 nanorods had a monoclinic single-crystalline structure.

Amorphous tungsten oxide has been prepared by ultrasound irradiation of a solution of tungsten hexacarbonyl W(CO)6 in diphenylmethane (DPhM) in the presence of an Ar (80%)–O2 (20%) gaseous mixture at 90 °C. Heating this amorphous powder at 550 °C under Ar yields snowflake-like dendritic particles consisting of a mixture of monoclinic and orthorhombic WO2 crystals. Annealing of the as-prepared product in Ar at 1000 °C causes the formation of a WO2–WO3 mixture containing nanorods (around 50 nm in diameter) and packs of these nanorods. Heating the product in air for 3 hours leads to triclinic WO3 crystal formation, with a basic size of 50–70 nm. The prepared oxides have been characterized by elemental analysis, X-ray powder diffraction measurements, FTIR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX).

Aromatic tertiary phosphine ligands having ortho -methoxy substituents reacted with Group 6 metal carbonyls to form complexes with monodentate bonding through the phosphorus atom. One tungsten hexacarbonyl derivative with two P-bonded phosphine ligands was also formed. The complexes were characterized by X-ray crystallography, 1 H, 13 C{ 1 H} and 31 P{ 1 H) NMR spectroscopy, IR spectroscopy and elemental analysis. The steric properties of the ligands were studied by molecular modelling methods. Metal–phosphorus bond distances correlate with cone angles of the phosphines.

The mononuclear tungsten pentacarbonyl complexes with 1,2-bis(4-pyridyl)ethane and 4,4′-bipyridine were synthesised by the irradiation, with a UV source, of solutions of tungsten hexacarbonyl and the relevant N-containing ligand. Both complexes were characterised by single-crystal X-ray diffraction and in both structures, the coordination geometry of the tungsten atom is slightly distorted from octahedral.

Tungsten (W) films were deposited on Si(100) from tungsten hexacarbonyl, [W(CO)6], by low-pressure chemical vapor deposition (CVD) in an ultra-high vacuum (UHV)-compatible reactor. The chemical purity, resistivity, crystallographic phase, and morphology of the deposited films depend markedly on the substrate temperature. Films deposited at 375°C contain approximately 80 at.% tungsten, 15 at.% carbon and 5 at.% oxygen. These films are polycrystalline β-W with a strong (211) orientation and resistivities of >1000 μΩ cm. Vacuum annealing at 900°C converts the metastable β-W to polycrystalline α-W, with a resistivity of approximately 19 μΩ cm. The resultant α-W films are porous, with small randomly oriented grains and nanoscale ( 95 at.%) polycrystalline α-W, with low resistivities (18–23 μΩ cm) and a tendency towards a (100) orientation. Vacuum annealing at 900°C reduces the resistivity to approximately 10 μΩ cm, and results in a columnar morphology with a very strong (100) orientation.

The cyclic ketones can be converted to their aldol-type condensation products by the W(CO)6/CCl4/UV system. The reaction was monitored by recording the IR and GC-MS spectra of the reaction mixture. The results support a mechanism that includes an intermediate carbene complex of tungsten.

The title complex has been obtained by reaction of the tetraethylammonium pentacyanopropenide with tungsten hexacarbonyl in acetone. Its crystal structure involves discrete [W(CO)5{C3(CN)5}]− anions in which the organic fragment is N-coordinated via one of the nitrogen atoms of a cyano group borne by one of the terminal carbon atoms of the allylic skeleton. The anion presents a distorted octahedral coordination with a W–N bond length [2.168(5) A] considerably longer than the W–C bond lengths [cis-W–C in the range 1.998(7)–2.068(4) A; trans-W–C 1.962(7) A]. Cyclic voltammograms of this complex, recorded in CH2Cl2 and CH3CN (Bu4NPF6 0.1 M), display a quasi-reversible reduction and irreversible oxidation waves.

Metal-organic chemical vapor deposition (MOCVD) using tungsten hexacarbonyl (W(CO) 6 ) and H 2 S as precursors was employed to prepare tungsten disulfide (WS 2 ) thin films on Si substrates. Various degrees of preferred orientation as characterized by the WS 2 crystallites with their basal planes grown parallel to the substrate ( c (=)) and non-parallel to the substrate ( c (∥)) were obtained. Raman scattering was applied to study the effects of preferred orientation in WS 2 thin films on the Raman processes. As the fraction of c (∥) crystallites increases in the thin film structure, a large second order Raman peak appeared on a shoulder of the A 1g mode to the lower wavenumbers. Based on the analysis previously provided (C. Sourisseau, F. Cruege, M. Fouassier, Chem. Phys. 150 (1991) 281), this peak was characterized by two phonon-coupling originating from longitudinal acoustic (LA) and transverse acoustic (TA) phonons at the K point of the Brillouin zone. Cross-section high resolution electron microscopy (HREM) revealed that the WS 2 thin films grew with c (=) near the interface, followed by the formation of non-parallel crystallite ( c (∥)) co-mixing with c (=). Transition from c (=) to c (∥) in the microstructure occurred smoothly, showing curvature in the lattice image. Occurrence of the localized curvature in the thin film microstructure seems to be responsible for the enhancement of the two phonon-coupling process.

Tungsten-rich layers have been produced by pyrolysing the hexacarbonyl vapour in hydrogen at atmospheric pressure. When formed at or below 500°C they are poorly crystalline and consist of tungsten in the β-form, while above this temperature they have the α-form. As in other variations of the pyrolysis, high levels of oxygen and carbon are observed, although these reduce with increasing temperature of deposition and with post-deposition plasma bombardment. Plasma treatment increases the proportion of the α-form.

The outcome of UV photolysis of W(CO)6 molecules isolated in a solid CH4 or Ar matrix in the presence of an alkyne RCCR′ (R,R′H,H; Me,H; or Me, Me) at ca. 20 K has been monitored by recording the IR and UV-vis absorption spectra of the deposit. The results indicate that irradiation with light having wavelengths near 313 nm results in the formation of the (η2-alkyne)tungsten pentacarbonyl complex, [(η2-RCCR′)W(CO)5], in addition to [X … W(CO)5] (X  CH4 or Ar), and free CO. In the case of a terminal alkyne, e.g. HCCH or MeCCH, however, photolysis under these conditions gives, in addition to the η2-alkyne complex and in significantly greater yield, what appears to be the vinylidene derivative [R(H)CCW(CO)5] (RH or Me). Prolonged irradiation with UV light (λ = ca. 313 or 369 nm) causes the various pentacarbonyl complexes to lose CO with the formation of tetracarbonyl species; prominent among the products issuing from the W(CO)5/C2H2 system are [(η2-HCCH)(η1-H2CC)W(CO)4] (in C2H2-rich matrices) and [(η2-HCCH)W(CO)4] in which the alkyne is acting formally as a 4e ligand. The results are significant in relation to the likely intermediate stages in the photocatalytic polymerization of terminal alkynes induced by tungsten hexacarbonyl.

Dialkylzirconocenes react with molybdenum or tungsten hexacarbonyl and iodine or NBS to form cyclopentadiene molybdenum or tungsten tricarbonyl iodine or bromide.

The successive reaction of chromium and tungsten hexacarbonyl, (CO)6M (M = Cr, W), with [NC(Ph)R]− and [Et3O]BF4 yields the alkylideneamino(ethoxy)carbene complexes (CO)5M[C(OEt)NC(Ph)R] (M = Cr (1), W (2); R = NMe2 (a), tBu (b)). Ethoxide abstraction from 1 and 2 affords 2-azoniaallenylidene complexes, {(CO)5M[CNC(Ph)R]}+BF4− (3/4). The complexes 3 and 4 are best described as resonance hybrids of several limiting structures. On the basis of the spectroscopic data of the complexes 3a and 4a the limiting structure of an iminium-substituted isocyanide complex dominates.

Chromium hexacarbonyl reacts with (Et2NCS2)2Y (Y  Se, Te) in the presence of Me3NO·2H2O to form Cr(S2CNEt2)3. Tungsten hexacarbonyl, under the same conditions, gives rise to WSe2(S2CNEt2)3·0.5H2O (1) and [W(S2CNEt2)4]2W6O19 (2). The structures of 1 and 2 were established by X-ray structural analysis. The tungsten in complex 1 has a distorted dodecahedron coordination. The structure of 2 is ionic, and contains the well known W6O192− anion and the W(S2CNEt2)4+ cation containing dodecahedral tungsten.

Intramolecular hydrogen bonding and cation π-interactions can be used to favour cis isomers of [W(CO)4(PRPh2)2](R=2-pyridyl or phenyl) type complexes. The changes in isomerization equilibrium can be switched by protonation or deprotonation of the 2-pyridyl groups.

Treatment of several alkyl-substituted dipropynylated benzenes in the presence of tungsten hexacarbonyl and 4-chlorophenol at 150°C leads to the formation of poly( para -phenyleneethynylene)s (PPEs). The obtained PPEs are of moderate molecular weights but form in good to excellent yields. Dihexyl-, dinonyl-, and didodecyl-PPE have been made by this route. It is the first time that a tungsten-containing in situ catalyst system is reported to be active for alkyne metathesis.

International audience; Synchrotron based photoemission spectroscopy was used to study the adsorption of tungsten hexacarbonyl on SiO2 surfaces modified by potassium. Results were compared with the ones obtained when no potassium was present. Experiments using W4f and Si2p intensities variations show that, at 140 K, the tungsten hexacarbonyl growth proceeds via a simultaneous multilayer mode for the two kinds of surfaces but with differences in compositions of growing layers. Indeed, it is evidenced that, even at cryogenic temperatures, the presence of potassium induces decomposition of a significant part of tungsten hexacarbonyl molecules through a strong interaction between tungsten and potassium atoms in opposition to potassium-free surface cases where W(CO)6 molecules are simply physisorbed. Additional irradiation of adsorbed molecules with photons coming from 0-order synchrotron radiation, subsequent going back to room temperature and additional thermal treatments up to about 700 K were then used to induce further decomposition of the adsorbed precursor. It allows as well to get rid of carbon and, finally, to stabilize different W-based species on the surface. The state of tungsten remaining on the surface is then strongly influenced by presence of potassium. When potassium is present, highly oxidized tungsten species are observed, whereas reduced species are mainly detected for potassium-free surfaces. Moreover, as diffusion of potassium is revealed during formation of tungsten phase, one should guess that potassium plays a crucial role in tungsten oxidation mechanism.

The reaction of tungsten hexacarbonyl with tetraethylammonium diethyldithiocarbamate in MeCN affords the tungsten(0) dithiocarbamato complex [Et 4 N][W(CO) 4 (S 2 CNEt 2 )] ( 1 ) and 1 reacts with tetraethylammonium tungsten tetrathiolate [Et 4 N] 2 WS 4 in warm MeCN (or MeOH) resulting in a new mixed-valence dinuclear tungsten-sulfur compound [Et 4 N] 2 [(OC) 4 WS 2 WS 2 ] ( 2 ). 1 and 2 were characterized by routine elemental analysis and IR spectroscopy, and their structures were determined from three-dimensional X-ray data. 1 crystallizes in the orthorhombic space group Pca 2 1 with a =19.516(2), b =8.147(1), c =14.338(1) A; V =2279.8 A 3 ; Z =4 D c =1.83 g/cm 3 ; R =0.046, R w =0.053 for 1766 independent reflections (I>3σ (I)). 2 crystallizes in the orthorhombic space group Pbcm with a =18.414(4), b =12.007(2), c =13.523(3) A; V =2989.7 A 3 ; Z =4; D c =1.93 g/cm 3 ; R =0.050, R w =0.055 for 2373 independent reflections (I>3σ(I)). The structure of 1 is similar to the Mo analog, [Mo(CO) 4 (S 2 CNEt 2 )]−, with W-S of 2.591(3) and 2.636(4) A and the structure of the anion of 2 consist of an octahedron around a low-valence tungsten atom and a tetrahedron with a high-valence tungsten atom in the center sharing an edge which is the line between the two bridged sulfur atoms. The W-W bond length is 3.0104(6) A and the bimetallic center WS 2 W is in a plane with WSW angles of 77.9(1) and 77.9(1)°. Cyclic voltammetry of 1 and 2 is presented and a CV study of 2 shows the electrochemistry on the two metal centers with different valences is different. Like another member of this family, [(OC) 4 MoS 2 WS 2 ] 2− , the existence of W→WS 4 electron delocalization in 2 is discussed.

Conjugated polymers with ferrocene units as pendants or as end-groups have been systhesised using the classical metathesis polymerisation catalyst W(CO)6 under photo-irradiation. The polymers are characterised by spectroscopic techniques and the redox-behaviour of these complexes have been examined by cyclic voltammetry. ? 2002 Elsevier Science B.V. All rights reserved.

The authors use a helium ion microscope (HIM) equipped with a tungsten hexacarbonyl gas injection system (GIS) to form tungsten-based pillars on carbon and silicon substrates by helium ion beam-induced deposition. Tungsten-based pillars with a width of ∼40 nm and height of ∼2 μm (aspect ratio of ∼50) are successfully fabricated using the HIM-GIS method. The pillars consist of face-centered cubic WC1−x and/or W2(C, O) grains. Columnar voids with a width of 1–15 nm form in the center of the pillars, suggesting that the pillars are continuously sputter-etched by the incident helium ion beam during deposition. In addition, the authors observe beam irradiation damage in the form of blistering of the Si substrate at the interface between the pillar and Si substrate. The columnar void width and Si blister height decreases as the volumetric growth rate of the pillars increases regardless of the deposition parameters. The authors consider that at least three phenomena compete during pillar formation, namely pillar deposition, sputter-etching, and Si blistering. Although there are numerous parameters involved in HIM-GIS deposition, it appears that the volumetric growth rate determines both the microstructure of the tungsten-based pillars and the degree of substrate damage.

Using three different precursors [MeCpPtMe3, Pt(PF3)4, and W(CO)6], an ultra-high vacuum surface science approach has been used to identify and rationalize the effects of substrate temperature and electron fluence on the chemical composition and bonding in films created by electron beam induced deposition (EBID). X-ray photoelectron spectroscopy data indicate that the influence of these two processing variables on film properties is determined by the decomposition mechanism of the precursor. For precursors such as MeCpPtMe3 that decompose during EBID without forming a stable intermediate, the film's chemical composition is independent of substrate temperature or electron fluence. In contrast, for Pt(PF3)4 and W(CO)6, the initial electron stimulated deposition event in EBID creates surface bound intermediates Pt(PF3)3 and partially decarbonylated Wx(CO)y species, respectively. These intermediates can react subsequently by either thermal or electron stimulated processes. Consequently, the chemical composition of EBID films created from either Pt(PF3)4 or W(CO)6 is influenced by both the substrate temperature and the electron fluence. Higher substrate temperatures promote the ejection of intact PF3 and CO ligands from Pt(PF3)3 and Wx(CO)y intermediates, respectively, improving the film's metal content. However, reactions of Pt(PF3)3 and Wx(CO)y intermediates with electrons involve ligand decomposition, increasing the irreversibly bound phosphorous content in films created from Pt(PF3)4 and the degree of tungsten oxidation in films created from W(CO)6. Independent of temperature effects on chemical composition, elevated substrate temperatures (>25?°C) increased the degree of metallic character within EBID deposits created from MeCpPtMe3 and Pt(PF3)4.

Aerosol assisted chemical vapour deposition (AACVD) reactions of tungsten hexacarbonyl, [W(CO)6], in acetone, methanol, acetonitrile and a 50 : 50 mixture of acetone and toluene resulted in the deposition of blue partially reduced WO3−x films which showed preferred orientation along the (0 1 0) direction. Films deposited solely from toluene, however, were composed of a mixture of tungsten metal and W3O. All films could be annealed to yellow randomly orientated crystalline monoclinic WO3. The films deposited from methanol had a morphology comprising of a network of randomly orientated needles, which is strikingly different to the agglomeration of spherical particles observed with the other solvents. The WO3 films functioned as gas sensitive resistors for the detection of NO2. Responses were recorded at minimum concentrations of 1.03 ppm of NO2, significantly exceeding those of commercial screen printed sensors.

The densities of a series of metal-organic compounds potentially suitable for metal-organic chemical vapor deposition, MOCVD, formation of metal interconnection films, were determined using a gas pycnometer which measures the pressure change when a gas (helium) is allowed to expand in the presence of a solid material whose density is to be determined. The solid material is contained in a calibrated chamber. Using the ideal gas equation, the volume of the solid material can be calculated, and thus it’s density. Densities are reported for silver neodecanoate, tungsten hexacarbonyl, and metal acetylacetonates and hexafluoroacetylacetonates of aluminum, chromium, cobalt, copper, magnesium, nickel, palladium, platinum, rhodium, and zinc.

The polymerization of phenylacetylene induced by u.v. irradiation of W(CO) 6 in carbon tetrachloride provided a polymer, in a virtually quantitative yield, whose molecular weight reached ∼1 × 10 5 . The polymerization did not occur without u.v. irradiation or in the absence of a halide such as carbon tetrachloride. The influence of reaction conditions was examined. The corresponding Mo(CO) 6 CCl 4 h v catalyst was less active, and the polymer molecular weight was ∼ × 10 4 . Cr(CO) 6 , Mn 2 (CO) 10 and Re 2 (CO) 10 were found to be ineffective. The polymers formed were dark brown to yellow solids, and had the structure, CHCPh. The polymerization mechanism was discussed in comparison with olefin metathesis.

The decacarbonylditungstate dianion, readily generated from tungsten hexacarbonyl and sodium amalgam, undergoes a facile reaction with thioketones to give (thioketone)pentacarbonyltungsten(0) complexes in good to excellent yields. The latter complexes, and the molybdenum analog, were formed by treatment of a thione with the chloride-bridged tungsten and molybdenum tricarbonylmetalates, [M 2 (CO) 6 Cl 3 ] 3− (M = W, Mo).

The relative stabilities of silver neodecanoate, tungsten hexacarbonyl, and a seriesof metal acetyl- and hexafluoroacetyl- acetonates, were determined using differential ther-mal analysis (DTA) and weight loss analysis. In general, the acetylacetonates decom-pose in the solid state at relatively low temperatures (100-200° C), with several of them exhibiting appreciable vapor pressures at temperatures below which their decomposi-tion rate is significant. Hexaf luoro derivatives of these compounds are, in general, more volatile and decompose at higher temperatures. The thermal decomposition behavior of palladium(II) acetylacetonate and palladium(II) hexafluoroacetylacetonate were each investigated using DTA at atmospheric pressure and under each compound’s equilib-rium or decomposition product(s) vapor pressure in conjunction with weight loss and residue composition analysis. At the heating rates employed, ≤2° C/min, palladium(II) acetylacetonate tends to decompose upon heating in either an inert or oxidizing atmo-sphere before significant quantities volatilize. On the other hand, palladium(II) hex-afluoroacetylacetonate tends to volatilize completely before any signs of decomposition are observed under the same conditions. Heating palladium(II) acetylacetonate in ar-gon, at ≤2° C/min, shows the onset of an endotherm at approximately 196° C, at the conclusion of which a product containing 75% palladium was found, the remainder com-prised of carbon, hydrogen and oxygen. In an oxidizing atmosphere at the above men-tioned heating rate, Palladium(II) acetylacetonate decomposes exothermically at 180° C yielding essentially pure palladium. Continued heating in oxygen, to 800° C results in pure PdO. At 900° C, the PdO decomposes yielding pure palladium. Depending upon the heating rates applied, one or two endotherms may be observed during the heating of palladium(II) hexafluoroacetylacetonate. Heating at 2° C/min in either an argon or ox-ygen atmosphere, results in an endothermic transition due to fusion at 105° C in argon (101° C in oxygen), followed by a second endothermic transition at 231° C in argon (223° C in oxygen), due to the normal boiling point being achieved. If heating rates are slow enough,e.g. 0.1° C/min, complete volatilization may occur before the normal boiling point is reached.

Thermogravimetric and Derivative Thermogravimetric Analyses have been carried out on different stoichiometric mixtures of W(CO)6 and (CH3)3NO·2H2O (TMNO) under nitrogen. The stuides indicate that the optimum reactant ratio (W:TMNO) is close to 1:4, at which there is a single-step weight loss in the region 50–90°C and a residue (ca. 13%) is left. The rapid loss in weight is attributed to the ready decomposition of the primary product W(CO)6-n(Me3N)n (n>1). At W : TMNO ratios, 1 : n, where n is smaller or greater than four, unchanged W(CO)6 on TMNO, respectively, were observed from the thermal profiles. The liberation of CO2 was quantified during separate experiments. The amount of gas released is proportional to the concentration of TMNO present. When the latter is present in a 15-fold excess, four moles of CO2 are released per mole of the parent hexacarbonyl.

The photo-induced degradation of Ph2CW(CO)5 in n-hexane solution has been investigated, and found to produce tungsten hexacarbonyl and tetraphenylethylene, as well as products of hydrogen abstraction, diphenylmethane and 1,1,2,2-tetraphenylethane. Yields of the organic products are dependent on the concentration of Ph2CW(CO)5, the olefin being favored in more concentrated solution. Similar products and trends were found when Ph2CW(CO)5 was thermally degraded in n-heptane. Ligand transfer of the diphenylcarbene ligand was achieved by photolyzing Ph2CW(CO)5 in diethyl fumarate, which produced diethyl 3,3-diphenyl1-1,2-cyclopropanedicarboxylate, and via a thermal reaction of Ph2CW(CO)5 with CpMn(CO)2(THF), which produced Ph2CMn(CO)2Cp. Photolysis of the latter carbene complex in n-haxane produced the same organic products as those obtained from the photolysis of Ph2CW(CO)5.

Chloride-bridged tungsten tricarbonylmetalates [(OC) 3 W(Cl) 3 W(CO) 3 ] 3− , obtainable in high yields from tungsten hexacarbonyl and tetraalkylammonium chlorides, with allyl halides give π-allylhalogenotungsten dicarbonyls. With phosphines reductive elimination of allylhalide yields bis- or tris-(phosphine)-tungsten-dicarbonyls L 2 W(PR 3 ) 2 (CO) 2 , LW(PR 3 )P 3 (CO) 2 (L = CH 3 CN). Substitution reactions of L with various ligands under mild conditions are described. IR and electronic spectra of more than twenty new compouonds are discussed and compared with corresponding compounds of molybdenum.