Molybdenum Hexacarbonyl Research Articles

Interaction of Mo(CO)6 and its derivative fragments with the Cu(001) surface: Influence on the decomposition process

A theoretical study on the adsorption and decomposition of molybdenum carbonyl on the copper (001) surface is reported. The adsorption structures and energies of Mo(CO)n molecules (n = 1 … 6) are computed systematically using density functional theory with Van der Waals corrections. By analyzing the energies of the various conformations, the main factors that determine the stable adsorption geometry are identified. Insight into the thermodynamics of decomposition is gained by calculating the reaction energy for dissociation of Mo(CO)n into Mo(CO)n−1 and CO. In the gas phase, this reaction is highly endothermic for all n. On the Cu surface, however, removal of the first CO group (n = 6) becomes strongly exothermic. The subsequent dissociation steps (n < 6), are endothermic even on the surface, but the reaction energies are much reduced. Dissociation is found energetically more favorable than desorption in all cases. The results clearly show that molybdenum carbonyl decomposition is strongly facilitated by the presence of the Cu surface. © 2014 Wiley Periodicals, Inc.

Efficient Catalytic Hydrogenation of N‐Unsubstituted Cyclic Imides to Cyclic Amines

AbstractThe hydrogenation of N‐unsubstituted cyclic imides to the corresponding cyclic amines has been performed selectively with heterogeneous catalysts obtained from rhodium and molybdenum carbonyl precursors. Various substrates were reduced in good to high yields and selectivities. Platinum‐based catalysts also proved to be efficient. Furthermore, gram‐scale experiments were performed and the catalysts could be recycled.

Molybdenum (0) and tungsten (0) carbonyl N-heterocyclic carbene complexes as catalyst for olefin epoxidation

A series of Mo(0) and W(0) carbonyl N-heterocyclic carbene (NHC) complexes containing monodentate NHC ligands with the formulae of M(CO)4(NHC)2 (NHC = IBz = 1,3-dibenzylimidazol-2-ylidene, M = Mo (1a), W (2a); NHC = InPr = 1,3-dipropylimidazol-2-ylidene, M = Mo (3), W (4a)) and M(CO)5(NHC) (NHC = IBz, M = Mo (1b), W (2b); NHC = InPr, M = W (4b); NHC = IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, M = Mo (5), W (6)) and the complexes containing chelating NHC ligands Mo(CO)4(PyNHC) (PyNHC = 3-methyl-1-picolylimidazol-2-ylidene (7)) and Mo(CO)3(Py2NHC) (Py2NHC = 1,3-dipicolylimidazol-2-ylidene (8)) have been synthesized and fully characterized. They show moderate catalytic activities towards cyclooctene epoxidation in the presence of tert-butyl hydroperoxide (TBHP). The stability of Mo–CNHC bond under oxidative condition has been investigated.

Microstructural analysis and transport properties of MoO and MoC nanostructures prepared by focused electron beam-induced deposition.

By electron-beam-induced deposition, we have succeeded in the direct fabrication of nanowires of molybdenum oxide (MoOx) and molybdenum carbide (MoC) on a SiO2 substrate set in a scanning electron microscope. In order to prepare MoOx specimens of high purity, a precursor gas of molybdenum hexacarbonyl [Mo(CO)6] is used, mixed with oxygen gas. On the other hand, MoC is grown by mixing H2O gas with the precursor gas. The electrical transport properties of the nanowires are investigated by the DC four-terminal method. A highly resistive MoOx nanowire prepared from an as-deposited specimen by annealing in air shows nonlinear current-voltage characteristics and a high photoconductivity. The resistivity ρ of an as-deposited amorphous MoC (a-MoC) nanowire takes its maximum at a temperature T ≈ 10 K and decreases to ≈ 0 with decreasing temperature. This behavior of ρ(T) indicates the possible occurrence of superconductivity in a-MoC nanowires. The characteristic of ρ(T) below the superconducting transition temperature Tc ≈ 4 K can be well explained by the quantum phase-slip model with a coherence length ξ(0) ≈ 8 nm at T = 0.

Synthesis and reactivity of oxygen ligated molybdenum(II) carbonyl complexes

Bis(acetylacetonate) and bis(tropolonate) complexes of MoII were synthesized by combining [NEt4][Mo(CO)4(I)3] and two equivalents of the ligand, followed by trapping with either an alkyne or phosphine. Alkyne complexes (trop)2Mo(CO)(PhCCH) (1b) and (acac)2Mo(CO)(PhCCR) (R=Me (2a), H (2b)) were characterized crystallographically. The alkyne ligands undergo rapid rotation at room temperature on the NMR time scale and the barrier to rotation for the butyne complexes (LX)2Mo(CO)(MeCCMe) (LX=trop (1c), acac (2c)) were measured by variable temperature NMR. The rotational barrier of the tropolonate derivative 1c is 1.6kcal/mol lower than that of the acetylacetonate derivative 2c despite the fact that trop is both smaller and less basic than acac. The coordinated alkynes will readily undergo exchange with free alkyne in solution and, on a slower time scale, the CO ligand can be displaced to form the bis(alkyne) species (LX)2Mo(RCCR)2 (4). The CO ligand of (LX)2Mo(CO)(PhCCH) can also be readily displaced by P(OMe)3 to form (LX)2Mo(P(OMe)3)(PhCCH), but larger phosphorus donors do not react. Alkyne complexes 1 and 2 will oxidize in air to the d2 species (LX)2Mo(O)(RCCR) in which the alkyne has been rotated perpendicular to the Mo–O bond and locked in position. The synthesis of the (LX)2Mo(CO) fragment reported here provides access to oxygen ligated low-valent Mo species which have thus far remained elusive.

ChemInform Abstract: Molybdenum Hexacarbonyl‐Catalyzed Condensation of Malononitrile with Ketones and Aldehydes.

Molybdenum hexacarbonyl activated with pyridine or morpholine catalyzes the condensation of malononitrile with ketones and aldehydes at 140 °C, which leads to alkylidenemalononitriles in 75–100% yield.

Molybdenum-Mediated Desulfurization of Thiols and Disulfides

We have successfully achieved the molybdenum hexacarbonyl [Mo(CO)₆] mediated desulfurization of thiols and disulfides. In this reaction, the sulfhydryl (SH) mercapto groups of aryl, benzyl, primary and secondary alkyl thiols, and S–S single bonds of disulfides can be removed. This reaction has high functional group tolerance and is not affected by steric hindrance. The results of the reactions in acetone-<i>d</i> ₆ suggest that the sources of hydrogen in the thiol and disulfide desulfurizations are the hydrogen atom(s) of a sulfhydryl group and acetone (solvent), respectively, and that the desulfurization proceeds via the formation of an organomolybdenum species.

ChemInform Abstract: Palladium‐Catalyzed Carbonylative Synthesis of Phthalimides from 1,2‐Dibromoarenes with Molybdenum Hexacarbonyl as Carbon Monoxide Source.

AbstractApplication of tert‐butylamine or unsubstituted aniline as well as heterocyclic dibromoaryl derivatives leads to formation of the corresponding amides and only trace amounts of the phthalimides.

Atomic Layer Deposited Molybdenum Nitride Thin Film: A Promising Anode Material for Li Ion Batteries

Molybdenum nitride (MoNx) thin films are deposited by atomic layer deposition (ALD) using molybdenum hexacarbonyl [Mo(CO)6] and ammonia [NH3] at varied temperatures. A relatively narrow ALD temperature window is observed. In situ quartz crystal microbalance (QCM) measurements reveal the self-limiting growth nature of the deposition that is further verified with ex situ spectroscopic ellipsometry and X-ray reflectivity (XRR) measurements. A saturated growth rate of 2 Å/cycle at 170 °C is obtained. The deposition chemistry is studied by the in situ Fourier transform infrared spectroscopy (FTIR) that investigates the surface bound reactions during each half cycle. As deposited films are amorphous as observed from X-ray diffraction (XRD) and transmission electron microscopy electron diffraction (TEM ED) studies, which get converted to hexagonal-MoN upon annealing at 400 °C under NH3 atmosphere. As grown thin films are found to have notable potential as a carbon and binder free anode material in a Li ion battery. Under half-cell configuration, a stable discharge capacity of 700 mAh g(-1) was achieved after 100 charge-discharge cycles, at a current density of 100 μA cm(-2).

Carbonylative annulation of unsaturated compounds using molybdenum hexacarbonyl: an efficient synthesis of 2(1H)-quinolones

Carbonylative annulation of unsaturated compounds using molybdenum hexacarbonyl: an efficient synthesis of 2(1H)-quinolones

N-Aryl Isoleucine Derivatives as Angiotensin II AT2 Receptor Ligands.

A novel series of ligands for the recombinant human AT2 receptor has been synthesized utilizing a fast and efficient palladium-catalyzed procedure for aminocarbonylation as the key reaction. Molybdenum hexacarbonyl [Mo(CO)6] was employed as the carbon monoxide source, and controlled microwave heating was applied. The prepared N-aryl isoleucine derivatives, encompassing a variety of amide groups attached to the aromatic system, exhibit binding affinities at best with Ki values in the low micromolar range versus the recombinant human AT2 receptor. Some of the new nonpeptidic isoleucine derivatives may serve as starting points for further structural optimization. The presented data emphasize the importance of using human receptors in drug discovery programs.

ChemInform Abstract: Microwave Assisted Efficient Aminocarbonylation of N‐Tosylhydrazones with Molybdenum Hexacarbonyl and Amines.

AbstractAn efficient aminocarbonylation of N‐tosylhydrazones in the presence of molybdenum hexacarbonyl is reported.

Atomic Layer Deposition of Molybdenum Oxide for Solar Cell Application

This work focuses on synthesis of molybdenum oxide (MoO3) by Atomic layer deposition (ALD) using molybdenum hexacarbonyl [Mo (CO)6] and ozone. In-situ growth characteresticswerestudied by Quartz Crystal Microbalance (QCM). ALD temperature window for this material lies between 165 to 175°C giving a maximum growth rate of 0.45 Å per ALD cycle. Negligible nucleation was found by QCM studyindicating a linear growth of the film. Effect of different oxidants on the growth rate is also studied.As-deposited film is amorphous in nature which converts to monoclinic-MoO3 after annealing as seen by taransmission electron microscopy.

Novel chemical route for atomic layer deposition of MoS₂ thin film on SiO₂/Si substrate.

Recently MoS₂ with a two-dimensional layered structure has attracted great attention as an emerging material for electronics and catalysis applications. Although atomic layer deposition (ALD) is well-known as a special modification of chemical vapor deposition in order to grow a thin film in a manner of layer-by-layer, there is little literature on ALD of MoS₂ due to a lack of suitable chemistry. Here we report MoS₂ growth by ALD using molybdenum hexacarbonyl and dimethyldisulfide as Mo and S precursors, respectively. MoS₂ can be directly grown on a SiO₂/Si substrate at 100 °C via the novel chemical route. Although the as-grown films are shown to be amorphous in X-ray diffraction analysis, they clearly show characteristic Raman modes (E(1)₂g and A₁g) of 2H-MoS₂ with a trigonal prismatic arrangement of S-Mo-S units. After annealing at 900 °C for 5 min under Ar atmosphere, the film is crystallized for MoS₂ layers to be aligned with its basal plane parallel to the substrate.

Unusual coordination of tetrylenes to molybdenum carbonyl fragments.

Reactions of the tetrylenes Ge(SAr(Me6))2 (1) (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2), and Sn(SAr(Me6))2 (2) with (Mo(CO)4(NBD) (NBD = bicyclo[2.2.1]hepta-2,5-diene) gave three new, unusual complexes [Mo(THF)(CO)3{Ge(SAr(Me6))2}] (3), [Mo(THF)(CO)3{Ge(SAr(Me6))2}] (4) and [Mo(CO)4{Sn(SAr(Me6))2}] (5) which display no significant Ge/Sn-Mo bonding. Instead the ligands are coordinated to molybdenum in a bidentate fashion via the thiolato sulfurs.

Reactions of (SiMe2)(SiRR′) doubly-bridged biscyclopentadienes (RR′ = MePh, Ph2) with iron and molybdenum carbonyls

In the reaction of the doubly-bridged biscyclopentadiene (C5H4(SiMe2))(C5H4(SiMePh)) (1b) with Fe(CO)5, migration of the bridging SiMe2 or SiMePh group from the ligand to an iron atom gives the corresponding compound (SiMePh)(η5-C5H3)(η5:η1-C5H3)[(SiMe2)Fe(CO)2][Fe(CO)2] (4) or (SiMe2)(η5-C5H3)(η5:η1-C5H3)[(SiMePh)Fe(CO)2][Fe(CO)2] (5), containing one Fe–Si bond. The reaction also affords the product [(η5-C5H4)2(SiMePh)]Fe2(CO)2(μ-CO)2 (6), in which the SiMe2 group is totally cleaved, and the corresponding doubly-bridged Fe–Fe bonded products [(η5-C5H3(SiMe2))(η5-C5H3(SiMePh))]Fe2(CO)4 (2 and 3) as a pair of isomers. A similar reaction of 1b with Mo(CO)6 only results in the SiMe2 cleaved product [(η5-C5H4)2(SiMePh)]Mo2(CO)6 (9), as well as the normal doubly-bridged Mo–Mo bonded complexes [(η5-C5H3(SiMe2))(η5-C5H3(SiMePh))]Mo2(CO)6 (7 and 8) as a pair of isomers. Reaction of the doubly-bridged biscyclopentadiene (C5H4(SiMe2))(C5H4(SiPh2)) (1c) with Fe(CO)5 or Mo(CO)6, similarly, yields the corresponding SiMe2 removed product (11 or 13) and the doubly-bridged dinuclear complex (10 or 12). The molecular structures of complexes 2, 4, 5 and 7 were determined by X-ray diffraction.

Palladium‐Catalyzed Carbonylative Synthesis of Phthalimides from 1,2‐Dibromoarenes with Molybdenum Hexacarbonyl as Carbon Monoxide Source

AbstractWe describe here a convenient and mild, carbon monoxide gas‐free palladium‐catalyzed procedure to obtain N‐substituted phthalimides with molybdenum hexacarbonyl as carbon monoxide precursor. These conditions tolerate a number of functional groups on the benzene ring as well as a number of amines and give the corresponding phthalimides in good to excellent yields.magnified image

Chemical Vapor Deposition of MoS2 Films

The MoS2 films were deposited on the titanium nitride (TiN) substrate using chemical vapor deposition (CVD) method. The molybdenum hexacarbonyl (Mo(CO)6) and hydrogen sulfide (H2S) as a precursor and reaction gas, respectively. Preliminary analysis of Mo(CO)6 which decomposed about 200 degree Celsius under low pressure condition was carried out using Fourier transform infrared spectroscopy (FT-IR). The MoS2 films deposited under the various substrate temperature, chamber pressure, and flow rate were analyzed using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. The result of Raman spectroscopy shows the bulk MoS2 Raman shift for samples deposited on the specific conditions.

Performance of Density Functional Theory for Second Row (4d) Transition Metal Thermochemistry.

The performances of 22 density functionals, including generalized gradient approximation (GGA), hybrid GGAs, hybrid-meta GGAs, and range-separated and double hybrid functionals, in combination with the correlation consistent basis sets and effective core potentials, have been gauged for the prediction of gas phase enthalpies of formation for the TM-4d set, which contains 30 second row transition metal-containing molecules. The enthalpies of formation determined by the 22 density functionals were compared to those generated via the relativistic pseudopotential correlation consistent Composite Approach (rp-ccCA), which has a goal of reproducing energies akin to those from CCSD(T,FC1)-DK/aug-cc-pCV∞Z-DK calculations. B3LYP/cc-pVTZ-PP optimized geometries were used in this study, though structures determined by other functionals also were examined. Of the functionals employed, the double hybrid functionals, B2GP-PLYP and mPW2-PLYP, yielded the best overall results with mean absolute deviations (MADs) from experimental enthalpies of formation of 4.25 and 5.19 kcal mol(-1), respectively. The GGA functionals BP86 and PBEPBE resulted in deviations from experiment of nearly 100 kcal mol(-1) for molecules such as molybdenum carbonyls. The ωB97X-D functional, which includes the separation of exchange energy into long-range and short-range contributions and includes a dispersion correction, resulted in an MAD of 6.52 kcal mol(-1).

Mo(CO)6 dissociation on Cu(111) stimulated by a Scanning Tunneling Microscope

The surface of Cu(111) was exposed to molybdenum hexacarbonyl Mo(CO)6 with monolayer coverage at temperature 160K and studied by a Scanning Tunneling Microscope. The monolayer structure has a hexagonal arrangement and forms a (√7×√7) R19 superlattice on the copper (111) plane. Upon repeated scanning the monolayer is transformed into a (1×2) superstructure with 3-fold oriented domains. The domains of (1×2) superstructure can change orientation under scanning according to 3-fold surface symmetry. From analysis of the domain mobility, it follows that CO groups of carbonyl fragments are organized in the (1×2) superstructure conditioning the domain reorientation. The observed structure transformation under scanning is a result of stimulated dissociation of molybdenum hexacarbonyl on the copper surface.