Tungsten Hexacarbonyl Research Articles

Heavy Pentaisopropylcyclopentadienyltriylenes and their Heterobimetallic Complexes.

A series of triylenes of the heavy group 13 elements gallium, indium and thallium, carrying the pentaisopropylcyclopentadienyl ligand is reported. The compounds were characterized in solution and in the solid-state and their donor ligand properties in heterobimetallic complexes were investigated, whereby a series of tungsten carbonyl complexes was isolated. Furthermore, a new synthetic route towards a previously described lithium-aluminum heterobimetallic dimetallocene is reported, which also enabled the isolation of a heterobimetallic polydecker of lithium and gallium.

Single Site W(0) versus Re(I)‐Dipyridophenazine‐ Based Conjugated Porous Polymer for CO2 Photoreduction

Herein, the synthesis and characterization of two robust tungsten and rhenium carbonyl complexes integrated into an organic polymer (CPP‐Re, CPP‐W) are reported. These polymers are obtained by a Suzuki coupling reaction between the corresponding dibromo metal‐carbonyl substituted dipyrido[3,2‐a:2′,3′‐c]phenazine complex and 1,3,5‐triphenylbenzene‐4′,4″,4″,4‴‐triboronic acid and integrated catalytic active sites and photosensitizer since they have not only nitrogen sites to coordinate metal active centers as rhenium or tungsten but photoactive units with good charge‐separating ability which can significantly improve the CO2 photoreduction reaction (CO2PRR). These polymers show similar activity in solid–gas CO2PRR in absence of sacrificial agents to produce syn gas (CO + H2) but CPP‐W selectivity to products change regarding CPP‐Re being able to produce also large amount of more demanding electron products such as methane and ethane. Moreover, the single‐site Re‐ or W‐CPP catalysts could prevent the dimerization of complexes that produces its deactivation. This work shows the potential of CPPs as matrices to support single active centers for heterogeneous catalysis.

Synthesis of polyhedral Pt-Pd-Ni nanobelts regulated by W(CO)6 and applied as a highly performing oxygen reduction reaction electrocatalyst

Pt-Pd-Ni polyhedral nanobelt (PNBs) composite catalysts are synthesized in presence of tungsten hexacarbonyl [W(CO)6] by a simple solvothermal method, combining both higher specific surface area and more index active site than the corresponding single-structure catalysts. The thermal decomposition of W(CO)6 plays a crucial role in the morphology formation. The tenuous composite with a moderate nanobelt width of 7.46 nm formed after heating for 6 h (Pt-Pd-Ni PNBs2) shows better ORR performance and durability than the ternary (Pt-Pd-Ni) and binary (Pt-Pd) single structures. It exhibits a mass activity of 1.49 (A mgPt−1), which only degrades by about 10.63 % after 50,000 durability cycles. The metal regulatory effects induced by the carbonyl compounds cause the contraction of the Pt-Pt bonds. Density functional theory calculations indicate that the compressive strain of Pt-Pd-Ni PNBs2 leads to a decrease in the d-band center and overpotential negatively shifted, thus provide a more sufficient and faster ORR proceeding process in thermodynamics, facilitating a higher energy conversion efficiency.

Focused Helium Ion and Electron Beam-Induced Deposition of Organometallic Tips for Dynamic Atomic Force Microscopy of Biomolecules in Liquid.

We demonstrate the fabrication of sharp nanopillars of high aspect ratio onto specialized atomic force microscopy (AFM) microcantilevers and their use for high-speed AFM of DNA and nucleoproteins in liquid. The fabrication technique uses localized charged-particle-induced deposition with either a focused beam of helium ions or electrons in a helium ion microscope (HIM) or scanning electron microscope (SEM). This approach enables customized growth onto delicate substrates with nanometer-scale placement precision and in situ imaging of the final tip structures using the HIM or SEM. Tip radii of <10 nm are obtained and the underlying microcantilever remains intact. Instead of the more commonly used organic precursors employed for bio-AFM applications, we use an organometallic precursor (tungsten hexacarbonyl) resulting in tungsten-containing tips. Transmission electron microscopy reveals a thin layer of carbon on the tips. The interaction of the new tips with biological specimens is therefore likely very similar to that of standard carbonaceous tips, with the added benefit of robustness. A further advantage of the organometallic tips is that compared to carbonaceous tips they better withstand UV-ozone cleaning treatments to remove residual organic contaminants between experiments, which are inevitable during the scanning of soft biomolecules in liquid. Our tips can also be grown onto the blunted tips of previously used cantilevers, thus providing a means to recycle specialized cantilevers and restore their performance to the original manufacturer specifications. Finally, a focused helium ion beam milling technique to reduce the tip radii and thus further improve lateral spatial resolution in the AFM scans is demonstrated.

Aerosol-Assisted Chemical Vapor Deposition of 2H-WS2 From Single-Source Tungsten Dithiolene Precursors.

The tungsten carbonyl dimethyldithiolene (dmdt) complexes W(CO)4(dmdt), W(CO)2(dmdt)2, and W(dmdt)3 were evaluated as potential single-source precursors for the chemical vapor deposition of WS2. The results of TGA-MS, DIP-MS, and pyrolysis with NMR analysis were consistent with a thermal decomposition pathway in which loss of 2-butyne through a retro[3+2]cycloaddition of the dithiolene ligand generated terminal sulfido ligands. Aerosol-assisted chemical vapor deposition onto silicon substrates was performed using all three complexes, yielding 2H-WS2 thin films as characterized by Raman spectroscopy and GI-XRD. Film morphology and elemental composition of the films were determined using SEM, EDS, and XPS. Four-point probe measurements afforded a film resistivity of 8.37 Ωcm for a sample deposited from W(dmdt)3 in toluene at 600 °C.

MOCVD Growth of Tungsten Ditelluride Thin Films

The growth of tungsten ditelluride (WTe2) thin films on c-plane sapphire substrates was demonstrated by metalorganic chemical vapor deposition (MOCVD) using tungsten hexacarbonyl (W(CO)6) and diethyltelluride (DETe) as precursors for W and Te, respectively, in a H2 carrier gas. The effects of substrate temperature, reactor pressure, precursor and carrier gas flow rates, and chalcogen-to-metal ratio on the WTe2 growth rate and film properties were determined. Substrate temperatures less than 500 °C were required to deposit WTe2 which was found to be beneficial to suppress simultaneous carbon deposition from the DETe precursor. The films exhibited a fine-grained morphology independent of growth temperature. The layered crystalline 1 T’ phase of WTe2 was confirmed using high resolution X-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (TEM) which revealed that the films were predominantly c-axis oriented with in-plane twist. X-ray photoelectron spectroscopy (XPS) demonstrated that the WTe2 films were stable in air for a few days but eventually exhibited oxidation.

Preparation, characterization and densification studies of W-Ag nanocomposites produced by chemical route

W-Ag has applications in a wide range of cutting-edge fields, counting heat sinks and microwave absorbers for micro—electronic components, electric arc ends, and filaments for welding processes, electrical contacts, and durable electronic connections. Chemical methods provide a number of benefits, including improved purity, and controlled particle size. The present study focused on the fabrication of W-Ag nano composites using chemical synthesis. W-Ag nanocomposites with average size less than 50 nm were synthesized using Tungsten hexacarbonyl (W(CO)6, and silver acetate (CH3-COOAg) as metal precursors in the present study. The W-Ag composites were sintered using conventional sintering. X-ray diffraction studies of as-prepared powders showed amorphous W-phase and FCC Ag, while sintered W-Ag composites exhibited crystalline BCC W and FCC Ag phase. The effect of sintering temperature on relative density and mechanical properties of W-Ag sintered compacts was investigated. Relative density in excess of 97.6%, 98.2% and 98.8% was achieved for W-20.3 wt.% Ag, W-30.1 wt.% Ag and W-39.8 wt.% Ag composites on conventional sintering at 1000°C for 1 h. Vickers hardness of 364 ± 10 and 320 ± 8 Hv and 279 ± 6 were achieved for W-20.3 wt.% Ag, W-30.1 wt.% Ag and W-39.8 wt.% Ag composite compacts respectively. The hardness value of W-Ag composites decreased with an increase in Ag content. The combination of properties realized in this study renders the composites suitable for automotive and heat sink applications.

(Decacarbonyl)(1-isopropyl-2-phenyl-1,2,5,6-tetrahydroacenaphtho [5,6-cd][1,2]diphosphole)ditungsten(0)

A binuclear tungsten(0) complex with an asymmetric bridging 1,2-diphosphole ligand was prepared by the photolysis of tungsten hexacarbonyl in the presence of 1-isopropyl-2-phenyl-1,2,5,6-tetrahydroacenaphtho [5,6-cd][1,2]diphosphole. The tungsten complex 1 was characterized by high resolution mass spectrometry, multinuclear NMR spectroscopy (1H, 13C, 31P), and elemental microanalysis. The structure of the trans isomer was resolved by single crystal X-ray diffraction, showing a slight elongation of the P−P bond upon coordination to the W(CO)5 groups.

Mid-infrared silicon metasurfaces for near-field enhancement of molecular fingerprints.

Mid-infrared dielectric metasurfaces are promising fundamental building blocks for integrated sensing with high sensitivity, compositional selectivity, and low loss. We have designed and fabricated a silicon metasurface with resonance properties in the 4∼5 µm mid-infrared region and a volume enhancement of up to 9 times. Benchmark FTIR characterizations of solutions of tungsten hexacarbonyl molecules showed a detection limit of 1 mg/mL without the usage of surface enrichment treatment. We further rationalize the detection limit of the molecules-nanostructure open interface with volume field enhancement analysis. Our results show that mid-infrared silicon metasurfaces may be a suitable platform for potential integration with microfluidic for in vivo detection.

Nucleation and coalescence of tungsten disulfide layers grown by metalorganic chemical vapor deposition

The nucleation of tungsten disulfide WS2 crystallites and coalescence behaviour of monolayer WS2 films grown on C-plane sapphire have been studied in a commercial AIXTRON close coupled showerhead metalorganic chemical vapor deposition (MOCVD) reactor using tungsten hexacarbonyl and di-tert-butyl sulfide as precursors. The influence of sapphire substrates offcut (both orientation and angle), as well as the substrate annealing conditions and growth temperature, on the nucleation and size of the WS2 domains has been investigated. A higher nucleation temperature combined with increased substrate annealing temperatures was found to promote an increase in the WS2 domain size. The dependence of surface coverage and coalescence behaviour of the WS2 domains on the growth duration has also been determined, allowing monolayer WS2 films with < 10 % bilayer to be obtained. Crystalline quality of the coalesced WS2 films has been assessed by grazing incidence XRD and misorientation mapping using 4D-scanning transmission electron microscopy, showing a slight in-plane misorientation of the crystallites in the WS2 monolayer. The electrical performance of the coalesced WS2 films was assessed using backgated TLM structures demonstrating mobility values of up to 5 cm2/Vs and a high Ion/Ioff ratio greater than 108.

TDDFT-DFT Theoretical Method and Topological Analysis to the Behavior Understanding of Two Tungsten Carbonyl Complexes

We present here a study based on Density Functional Theory (DFT) calculations, to contribute to the understanding of the complexes behavior based on tungsten carbonyls ([W(C7H7NS)(CO)5], [W ( C3H6N2S)(CO)5 ] ), which consider as targets molecules of biological interest and easily detectable probes by IR spectroscopy. The results showed good agreements between the calculated and experimental values of the geometric parameters for the two complexes. A peak in the IR spectrum at 2030 cm-1 is due to the stretching of the C-O triple bond, according to the AIM analysis (0.07 andlt;ρ andlt;0.15 ), the existence of an intermediate interaction between the tungsten and the CO ligand. Moreover, these complexes are stable, the spectra of TD–DFT analysis showed these complexes absorb in the same domain of wavelengths, through absorption features at about 110-160 nm, characterized by natural transitions of HOMO/LUMO; of type MLCT for both complexes

Одностадийный синтез смеси наночастиц WC-=SUB=-1-x-=/SUB=- и гибридного наноматериала на основе многостенных углеродных нанотрубок с нанопокрытиями WC-=SUB=-1-x-=/SUB=-

By the method of chemical vapor deposition of tungsten hexacarbonyl at atmospheric pressure in an argon flow has been used to obtain promising fillers for aluminum matrix composite materials in the form of a mixture of nanoparticles of non-stoichiometric cubic tungsten carbide (WC1-x) and hybrid nanomaterials based on multi-walled carbon nanotubes decorated with nonstoichiometric cubic tungsten carbide. The influence of chemical vapor deposition (CVD) parameters on the morphology of samples was studied and the optimal synthesis conditions were selected. The structure and composition of the synthesized materials were studied by electron microscopy and X-ray phase analysis

Tungsten doped diamond shells for record neutron yield inertial confinement fusion experiments at the National Ignition Facility

We report on fabrication and characterization of layered, tungsten doped, spherical about 2 mm diameter microcrystalline diamond ablator shells for inertial confinement fusion (ICF) experiments at the National Ignition Facility. As previously reported, diamond ICF ablator shells can be fabricated by chemical vapor deposition (CVD) on solid spherical silicon mandrels using an ellipsoidal microwave plasma reactor. In the present work, we further developed these ablator shells by embedding a W-doped diamond layer sandwiched between two undoped diamond regions. W incorporation in diamond was achieved by adding tungsten hexacarbonyl to the CH4/H2 CVD feed gas. We observe that the W doping concentration decreases with increasing deposition rate which, in turn, is controlled by adjusting the total gas pressure. Cross sectional microstructural analysis reveals sharp interfaces between doped and undoped regions of the diamond shell and uniform W distribution with concentrations up to about 0.3 at.%. At higher W concentrations (>0.3 at.%) formation of tungsten carbide precipitates is observed. Using a 3‐shock 1.6 MJ laser pulse, the targets described in this work produced the first laser driven implosion to break the 1 × 1016 neutron yield barrier, followed by experiments (described in future publications) with similar targets and slightly more laser energy producing yields as high as 4 × 1017.

Controlled CO labilization of tungsten carbonyl precursors for the low-temperature synthesis of tungsten diselenide nanocrystals

We report a low-temperature colloidal synthesis of WSe2 nanocrystals from tungsten hexacarbonyl and diphenyl diselenide in trioctylphosphine oxide (TOPO). We identify TOPO-substituted intermediates, W(CO)5TOPO and cis-W(CO)4(TOPO)2 by infrared spectroscopy. To confirm these assignments, we synthesize aryl analogues of phosphine-oxide-substituted intermediates, W(CO)5TPPO (synthesized previously, TPPO = triphenylphosphine oxide) and cis-W(CO)4(TPPO)2 and fac-W(CO)3(TPPO)3 (new structures reported herein). Ligation of the tungsten carbonyl by either the alkyl or aryl phosphine oxides results in facile labilization of the remaining CO, enabling low-temperature decomposition to nucleate WSe2 nanocrystals. The reactivity in phosphine oxides is contrasted with syntheses containing phosphine ligands, where substitution results in decreased CO labilization and higher temperatures are required to induce nanocrystal nucleation.

Hydrostannylation of Olefins by a Hydridostannylene Tungsten Complex

Reaction of the aryltin(II) hydride {AriPr6Sn(μ-H)}2 (AriPr6 = −C6H3-2,6-(C6H2-2,4,6-iPr3)2) with two equivalents of the tungsten carbonyl THF complex, [W(CO)5(THF)], afforded the divalent tin hydride transition metal complex, W(CO)5{Sn(AriPr6)H}, (1). Complex 1 reacted rapidly with ethylene, or propylene under ambient conditions to yield the corresponding hydrostannylated organometallic species, W(CO)5{Sn(AriPr6)(Et)} (2), or W(CO)5{Sn(AriPr6)(nPr)} (3), via olefin insertion into the Sn–H bond. Treatment of 1 with the Lewis base dbu (dbu = 1,8-diazabicycloundec-7-ene) afforded the Lewis acid–base complex, W(CO)5{Sn(AriPr6)(dbu)H} (4), indicating that the Lewis acidity of the tin atom is preserved in 4. The complexes were characterized by X-ray crystallography, and by UV–visible, FT-IR, and multinuclear NMR spectroscopies. DFT calculations suggest hydrostannylation of ethylene with 1 proceeds via coordination of ethylene to the tin atom, then insertion into the Sn–H bond. Further computational study on the reactivity of 1 toward Ph3SiH indicated that the rate-determining step involves the metathesis reaction of a Sn–C/Si–H bond with a very high energy barrier of 71.3 kcal/mol. The calculated proton abstraction product of 1 with dbu, [W(CO)5{Sn(AriPr6)}]+[H(dbu)]−, is 18.2 kcal/mol less stable than the observed coordination product 4.

Front Cover: Mechanistic and Kinetic Investigations of ON/OFF (Photo)Switchable Binding of Carbon Monoxide by Chromium(0), Molybdenum(0) and Tungsten(0) Carbonyl Complexes with a Pyridyl‐Mesoionic Carbene Ligand (Chem. Eur. J. 51/2022)

Front Cover: Mechanistic and Kinetic Investigations of ON/OFF (Photo)Switchable Binding of Carbon Monoxide by Chromium(0), Molybdenum(0) and Tungsten(0) Carbonyl Complexes with a Pyridyl‐Mesoionic Carbene Ligand (Chem. Eur. J. 51/2022)

Mechanistic and Kinetic Investigations of ON/OFF (Photo)Switchable Binding of Carbon Monoxide by Chromium(0), Molybdenum(0) and Tungsten(0) Carbonyl Complexes with a Pyridyl-Mesoionic Carbene Ligand.

Invited for the cover of this issue are Gereon Niedner-Schatteburg, Biprajit Sarkar and co-worker at TU Kaiserslautern and the University of Stuttgart. The image depicts the selective dissociation of an axial CO from a metal complex. Read the full text of the article at 10.1002/chem.202201038.

In Situ Time-of-Flight Mass Spectrometry of Ionic Fragments Induced by Focused Electron Beam Irradiation: Investigation of Electron Driven Surface Chemistry inside an SEM under High Vacuum.

Recent developments in nanoprinting using focused electron beams have created a need to develop analysis methods for the products of electron-induced fragmentation of different metalorganic compounds. The original approach used here is termed focused-electron-beam-induced mass spectrometry (FEBiMS). FEBiMS enables the investigation of the fragmentation of electron-sensitive materials during irradiation within the typical primary electron beam energy range of a scanning electron microscope (0.5 to 30 keV) and high vacuum range. The method combines a typical scanning electron microscope with an ion-extractor-coupled mass spectrometer setup collecting the charged fragments generated by the focused electron beam when impinging on the substrate material. The FEBiMS of fragments obtained during 10 keV electron irradiation of grains of silver and copper carboxylates and shows that the carboxylate ligand dissociates into many smaller volatile fragments. Furthermore, in situ FEBiMS was performed on carbonyls of ruthenium (solid) and during electron-beam-induced deposition, using tungsten carbonyl (inserted via a gas injection system). Loss of carbonyl ligands was identified as the main channel of dissociation for electron irradiation of these carbonyl compounds. The presented results clearly indicate that FEBiMS analysis can be expanded to organic, inorganic, and metal organic materials used in resist lithography, ice (cryo-)lithography, and focused-electron-beam-induced deposition and becomes, thus, a valuable versatile analysis tool to study both fundamental and process parameters in these nanotechnology fields.

Mechanistic and Kinetic Investigations of ON/OFF (Photo)Switchable Binding of Carbon Monoxide by Chromium(0), Molybdenum(0) and Tungsten(0) Carbonyl Complexes with a Pyridyl‐Mesoionic Carbene Ligand

This work tackles the photochemistry of a series of mononuclear Cr0, Mo0 and W0 carbonyl complexes containing a bidentate mesoionic carbene ligand of the 1,2,3‐triazol‐5‐ylidene type. FTIR spectroscopy, combined with density functional theory calculations, revealed a clean photo‐induced reaction in organic solvents (acetonitrile, pyridine, valeronitrile) to give mainly one photoproduct with monosubstitution of a carbonyl ligand for a solvent molecule. The highest photodissociation quantum yields were reached for the Cr0 complex under UV irradiation (266 nm). Based on previous investigations, the kinetics of the dark reverse reactions have now been determined, with reaction times of up to several hours in pyridine. Photochemical studies in the solid state (KBr matrix, frozen solution) also showed light‐induced reactivity with stabilization of the metastable intermediate with a free coordination site at very low temperature. The identified reactive species emphasizes a mechanism without ligand–sphere reorganization.

Dynamics in tris(pentafluoroethyl)trifluorophosphate (FAP) anion based ionic liquids: A 2D-IR study with tungsten hexacarbonyl

Ultrafast two-dimensional infrared spectroscopy (2D-IR) measurements for tungsten hexacarbonyl, W(CO)6, has been performed in two fluoroalkylphosphate ([FAP])-based ultrahigh hydrophobic, ionic liquids, namely, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate ([EMIM][FAP]) and 1-(hexyl)-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM][FAP]) to probe their local structure and dynamics. To understand the effect of FAP anion on the dynamics, a relatively less hydrophobic [PF6-] anion has been introduced in the form of [HMIM][PF6]. While the linear IR spectra records some influence of anion in terms of spectral shifts, the alkyl chain length of the cation seems to have no significant influence on the spectral peak position; and even the spectral broadening is found to be in the similar range. Further, vibrational population relaxation dynamics and vibrational anisotropy decay also does not show any significant variation due to difference in constituent of these ionic liquids as well as its solvent properties, such as, viscosity. Finally, 2D-IR spectra show large variation in the spectral shapes with waiting times, which qualitatively remains similar in all the tested ionic liquids. The frequency-fluctuation correlation function measured from 2D-IR spectra displays a bi-exponential decay with the shorter time-constant dependent on the identity of the anion, and has been attributed to the ion-rattling motion, whereas, the longer component has been found to be invariant with the identity of ionic liquid, and has been attributed to ion-cage motions which is in line with previous MD simulations as well as previous experimental measurements, using ionic vibrational probe. Overall, 2D-IR spectroscopy, in combination with this neutral and hydrophobic probe, W(CO)6 provides a unique opportunity to understand the local structural dynamics of this ultrahigh hydrophobic ionic liquid which are otherwise not accessible by hitherto explored ionic vibrational probes.