MoCl Research Articles

One-Step Hydrothermal Synthesis of MoS<sub>2</sub> Nano-Flowers with High Surface Area and Crystalline

One-step and controlled pH hydrothermal synthesis of transition metal disulfide using double molybdenum sources to synthesize MoS2 nano-flowers at low temperature was first reported. Anhydrous molybdenum pentachloride (MoCl5) and four sulfur ammonium molybdate ((NH4) 6Mo7O24•4H2O) were the molybdenum source and CS (NH2) 2 was the sulfur source. Through hydrothermal method, MoS2 was obtained at 180 °C. The pH value of system was controlled by adjusting the molar ratio of MoCl5 and (NH4) 6Mo7O24•4H2O. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area (BET) and transmission electron microscopy (TEM). The results show that the products were hexagonal MoS2 with a high crystalline and flower-like structure consisted of small particles. The thickness of petals is a few to tens of nanometers. By changing the molar ratio of molybdenum sources, the resultant phase from the mixed phase transited to the pure phase and the purity of synthetic MoS2 crystal increaseed.

Synthesis and characterization of molybdenum‐modified polycarbosilane for SiC(Mo) ceramics

AbstractA novel molybdenum‐containing polycarbosilane, polymolybdenocarbosilane (PMoCS), for SiC(Mo) fiber has been synthesized from polysilacarbosilane (PSCS) and MoCl5 as raw materials. The synthesis conditions is investigated. Characterization performed on the as‐synthesized PMoCS includes Fourier Transformed Infrared Spectroscopy (FT IR), gel‐permeation chromatography (GPC), X‐ray photoelectron spectroscopy (XPS), 1H NMR, and 29Si NMR, respectively. The polymer‐to‐ceramic conversion is studied with thermogravimetric analysis (TGA) and X‐ray diffraction (XRD). Preliminary research on the melt spinnability of PMoCS is carried out. The results show that the synthesis reaction is temperature‐dependent. Mo exists mainly as SiMo bonds. The reaction mechanism is believed to involve HCl elimination between SiH and MoCl, and followed by the Kumada rearrangement. The ceramic yield of PMoCS, prepared with 10 wt % MoCl5, is approximately 78.5% at 1200°C in a N2 flow. The XRD results suggest that ceramics pyrolyzed in the range of 800–1000°C are all amorphous, while β‐SiC and β‐MoSi2 crystals are observed at 1200 and 1400°C, respectively. The conversion from β‐MoSi2 to α‐MoSi2 is almost completed at 1600°C. PMoCS is melt spinnable into flexible and uniform green fibers with the diameters about 13.4 μm to 12.2 μm. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Salt-flux synthesis of complex oxides: Cs0.33MoO3, CsFe(MoO4)2, and the inverse salt-inclusion phase Cs2Mo0.65O0.21Cl5.44

Recent work on the growth of complex oxides in salt fluxes is reviewed. Single crystals of Cs0.33MoO3, CsFe(MoO4)2 and the new phase, Cs2Mo0.65O0.21Cl5.44, have been grown from the reaction of metal oxides Fe2O3, MoO3 and molybdenum powder in a eutectic CsCl/NaCl flux. Cs0.33MoO3 is one of the known molybdenum bronzes, featuring mixed valent molybdenum ions. CsFe(MoO4)2 has a layered KAl(MoO4)2 structure, which consists of infinite slabs of corner-sharing MoO4 and FeO6 polyhedra separated by layers of Cs+ cations. Cs2Mo0.65O0.21Cl5.44 forms with a new structure type (orthorhombic, Cmcm, a = 7.434(1) Å, b = 17.330(3) Å, c = 8.074(1) Å, Z = 4) which is comprised of isolated [Mo(O/Cl)Cl5] octahedra embedded in a distorted CsCl matrix. Magnetic susceptibility measurements indicate antiferromagnetic ordering for both CsFe(MoO4)2 (T N = 4.5 K) and Cs2Mo0.65O0.21Cl5.44 (T N = 7 K).

Water-Soluble Mo3S4 Clusters Bearing Hydroxypropyl Diphosphine Ligands: Synthesis, Crystal Structure, Aqueous Speciation, and Kinetics of Substitution Reactions

The [Mo(3)S(4)Cl(3)(dhprpe)(3)](+) (1(+)) cluster cation has been prepared by reaction between Mo(3)S(4)Cl(4)(PPh(3))(3) (solvent)(2) and the water-soluble 1,2-bis(bis(hydroxypropyl)phosphino)ethane (dhprpe, L) ligand. The crystal structure of [1](2)[Mo(6)Cl(14)] has been determined by X-ray diffraction methods and shows the typical incomplete cuboidal structure with a capping and three bridging sulfides. The octahedral coordination around each metal center is completed with a chlorine and two phosphorus atoms of the diphosphine ligand. Depending on the pH, the hydroxo group of the functionalized diphosphine can substitute the chloride ligands and coordinate to the cluster core to give new clusters with tridentate deprotonated dhprpe ligands of formula [Mo(3)S(4)(dhprpe-H)(3)](+) (2(+)). A detailed study based on stopped-flow, (31)P{(1)H} NMR, and electrospray ionization mass spectrometry techniques has been carried out to understand the behavior of acid-base equilibria and the kinetics of interconversion between the 1(+) and the 2(+) forms. Both conversion of 1(+) to 2(+) and its reverse process occur in a single kinetic step, so that reactions proceed at the three metal centers with statistically controlled kinetics. The values of the rate constants under different conditions are used to discuss on the mechanisms of opening and closing of the chelate rings with coordination or dissociation of chloride.

Synthesis of Highly Functionalized 9,10-Phenanthrenequinones by Oxidative Coupling Using MoCl5

The strong oxidative power of molybdenum pentachloride gives rise to an efficient oxidative C-C bond formation of benzil derivatives to the corresponding 9,10-phenanthrenequinones. A highly complementary method to previous approaches was developed. The required derivatives are accessible in a modular fashion and in excellent yields. By this approach the orchid-derived natural product cypripediquinone A was synthesized for the first time.

Triple bridged anionic dimetallic complexes from cis-[Mo(η3-methallyl)Cl(CO)2(NCMe)2] and pyrazolates

The reactions of cis-[Mo(η3-methallyl)Cl(CO)2(NCMe)2] and 0.5 equivalents of tetra-n-butylammonium salts of pyrazolate (pz), 3,5-dimethylpyrazolate (dmpz) or indazolate (inz) lead to NnBu4[{Mo(η3-methallyl)(CO)2(μ-Cl)}2(μ-pz*)] (pz* = pz, dmpz, inz), where the bridging pyrazolato is coordinated trans to the allyl group and both bridging chlorido ligands are coordinated trans to the carbonyls.

On the Structure of β-Molybdenum Dichloride

The structure of β-molybdenum dichloride is compared with that of TcCl(2) using EXAFS spectroscopy. For TcCl(2), the Tc atom is surrounded by Tc atoms at 2.13(2), 3.45(3), 3.79(4), and 4.02(4) Å. For β-MoCl(2), the Mo is surrounded by Mo atoms at 2.21(2), 2.91(3), and 3.83(4) Å. The latter distances are consistent with the presence of an [Mo(4)Cl(12)] unit in the solid state, one constituted by two triply Mo-Mo-bonded [Mo(2)Cl(8)] units. First-principles calculations show that β-MoCl(2) with the TcCl(2) "structure type" is less stable than α-MoCl(2) (Mo(6)Cl(12)) or [Mo(4)Cl(12)] edge-sharing clusters.

Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl)(PMe3)3.

The reaction of (ArN=)MoCl(2)(PMe(3))(3) (Ar = 2,6-diisopropylphenyl) with L-Selectride gives the hydrido-chloride complex (ArN=)Mo(H)(Cl)(PMe(3))(3) (2). Complex 2 was found to catalyze the hydrosilylation of carbonyls and nitriles as well as the dehydrogenative silylation of alcohols and water. Compound 2 does not show any productive reaction with PhSiH(3); however, a slow H/D exchange and formation of (ArN=)Mo(D)(Cl)(PMe(3))(3) (2(D)) was observed upon addition of PhSiD(3). Reactivity of 2 toward organic substrates was studied. Stoichiometric reactions of 2 with benzaldehyde and cyclohexanone start with dissociation of the trans-to-hydride PMe(3) ligand followed by coordination and insertion of carbonyls into the Mo-H bond to form alkoxy derivatives (ArN=)Mo(Cl)(OR)(PMe(2))L(2) (3: R = OCH(2)Ph, L(2) = 2 PMe(3); 5: R = OCH(2)Ph, L(2) = η(2)-PhC(O)H; 6: R = OCy, L(2) = 2 PMe(3)). The latter species reacts with PhSiH(3) to furnish the corresponding silyl ethers and to recover the hydride 2. An analogous mechanism was suggested for the dehydrogenative ethanolysis with PhSiH(3), with the key intermediate being the ethoxy complex (ArN=)Mo(Cl)(OEt)(PMe(3))(3) (7). In the case of hydrosilylation of acetophenone, a D-labeling experiment, i.e., a reaction of 2 with acetophenone and PhSiD(3) in the 1:1:1 ratio, suggests an alternative mechanism that does not involve the intermediacy of an alkoxy complex. In this particular case, the reaction presumably proceeds via Lewis acid catalysis. Similar to the case of benzaldehyde, treatment of 2 with styrene gives trans-(ArN=)Mo(H)(η(2)-CH(2)═CHPh)(PMe(3))(2) (8). Complex 8 slowly decomposes via the release of ethylbenzene, indicating only a slow insertion of styrene ligand into the Mo-H bond of 8.

Tricarbonylchlorido(η5-cyclopentadienyl)molybdenum(II)

The structure of the title compound, [Mo(C5H5)Cl(CO)3], reveals a pseudo-square-pyramidal piano-stool coordination around the MoII ion, which is surrounded by a cyclo­penta­dienyl ring, three carbonyl groups and a chloride ligand.

Catalytic hydroboration by an imido-hydrido complex of Mo(iv)

The imido-hydrido complex (ArN)Mo(H)(Cl)(PMe(3))(3) catalyses a variety of hydroboration reactions, including the first example of catalytic addition of HBCat to nitriles to form the bis(borylated) amines RCH(2)N(BCat)(2). The latter species easily undergoes chemoselective coupling with aldehydes R'C(O)H to yield imines RCH(2)N=C(H)R'.

Oxidative transformation of aryls using molybdenum pentachloride

Molybdenum pentachloride combines a strong Lewis acid character with an unusually high oxidation potential creating a powerful reagent for oxidative transformations. Since the oxidative coupling reaction of aryls is induced at an extraordinarily high reaction rate, a variety of labile groups, e.g. iodo, tert-alkyl, etc., are tolerated on the aromatic core. Furthermore, the co-formed molybdenum salts can either be exploited for template effects to obtain uncommon geometries in a preferred manner, or redox-play starts after aqueous workup. Therefore MoCl(5) represents a unique and easily available reagent.

Theoretical Elucidation of a Classic Reaction: Protonation of the Quadruple Bond of the Octachlorodimolybdate(II,II) [Mo2Cl8]4– Anion

The protonation reaction of the unbridged quadruple metal-metal bond of [Mo(2)Cl(8)](4-) anion producing the triply bonded hydride [Mo(2)(μ-H)(μ-Cl)(2)Cl(6)](3-) is studied by accurate Density Functional Theory computations. The reactant, product, stable intermediates, and transition states are located on the potential energy surface. The water solvent is explicitly included in the calculations. Full reaction profiles are calculated and compared to experimental data. The mechanism of the reaction is fully elucidated. This involves two steps. The first is a proton transfer from an oxonium ion to the quadruple bond, being rate determining. The second, involves the internal rearrangement of chlorine atoms and is much faster. Activation energies with a mean value of 19 kcal/mol are calculated, in excellent agreement with experimental values.

μ-Oxido-bis[chlorido(4,4′-di-tert-butyl-2,2′-bipyridine-κ2N,N′)dioxidomolybdenum(VI)] 0.2-hydrate

The title hydrate, [Mo2Cl2O5(C18H24N2)2]·0.2H2O, has been isolated as the oxidation product of [Mo(η3-C3H5)Cl(CO)2(di-t-Bu-bipy)] (where di-t-Bu-bipy is 4,4′-di-tert-butyl-2,2′-bipyridine). A μ-oxide ligand bridges two similar MoCl(di-t-Bu-bipy)O2 units, having the terminal oxide ligands mutually cis, and the chloride and μ-oxide trans to each other. In the binuclear complex, the coordination geometries of the metal atoms can be described as highly distorted octa­hedra. Individual complexes co-crystallize with a partially occupied water mol­ecule of crystallization (occupancy factor = 0.20; H atoms not located), with the crystal packing being mediated by the need to effectively fill the available space. A number of weak C—H⋯O and C—H⋯Cl inter­actions are present.

Synthesis, characterization, and DNA binding of the biologically relevant novel cationic molybdenum(VI)–glutathione complex [Mo(GS)(Cl)(H2O)]Cl2

The complex [Mo(GS)(Cl)(H2O)]Cl2 (MoG) was synthesized in aqueous medium and its composition has been determined by elemental and thermogravimetric analysis. Binding modes were determined by 1H NMR, 13C NMR, mass, and FT-IR spectrometry. The molecular formula was confirmed by mass spectral analysis. The molecular weight of the complex determined by the Rast camphor method also supports the formulation M r = 525. This molecular formula demands the compound to be a 1:2 electrolyte, which is also supported by the conductance measurement, its value being 210 Ω−1 cm2. The compound is found to be diamagnetic, indicating that the molybdenum is in the +6 oxidation state (d0). The binding of MoG with calf thymus DNA was studied by spectroscopic titration. The interaction ratio was determined by monitoring the DNA 260 nm band as well as the S → Mo LMCT band of the complex observed at 225 nm. The interaction ratio calculated from the above studies was found to be 1:0.70 (DNA:MoG) in both cases, while the binding constant of DNA–MoG was found to be (4.8 ± 0.5) × 105 M−1. The binding constant data indicate that the binding nature is intercalative.

Crystal Structure of Na3MoCl6

The ternary chloride Na3MoCl6 is obtained as red crystals from a disproportionation reaction of molybdenum dichloride, {Mo6}Cl12, in an acidic NaCl/AlCl3 melt at 350 °C. The crystal structure (trigonal, P-31c, a = 687.1(1), c = 1225.3(2) pm, Z = 2, V = 501,0(1) 106 pm3) is that of Na3CrCl6: within a hexagonal closest-packing of chloride ions two thirds of the octahedral voids are filled between the AB double layers with Na+/Mo3+, and between the BA layers with Na+.

Extending the Family of Titanium Heterometallic–oxo–alkoxy Cages

Here we investigate the synthesis of high-nuclearity heterometallic titanium oxo-alkoxy cages using the reactions of metal chlorides with [Ti(OEt)(4)] or the pre-formed homometallic titanium-oxo-alkoxy cage [Ti(7)O(4)(OEt)(20)] (A). The octanuclear Ti(7)Co(II) cage [Ti(7)CoO(5)(OEt)(19)Cl] (1) (whose low-yielding synthesis we reported earlier) can be made in better yield, reproducibly by the reaction of a mixture of heptanuclear [Ti(7)O(4)(OEt)(20)] (A) and [KOEt] with [Co(II)Cl(2)] in toluene. A alone reacts with [Co(II)Cl(2)] and [Fe(II)Cl(2)] to form [Ti(7)Co(II)O(5)(OEt)(18)Cl(2)] (2) and [Ti(7)Fe(II)O(5)(OEt)(18)Cl(2)] (3), respectively. Like 1, compounds 2 and 3 retain the original Ti(7) fragment of A and the II-oxidation state of the transition metal ions (Tm). In contrast, from the reaction of [Ti(OEt)(4)] with [Cr(II)Cl(2)] it is possible to isolate [Ti(3)Cr(V)O(OEt)(14)Cl] (4) in low yield, containing a Ti(3)Cr(V) core in which oxidation of Cr from the II to V oxidation state has occurred. Reaction of [Mo(V)Cl(5)] with [Ti(OEt)](4) in [EtOH] gives the Ti(8)Mo(V)(4) cage [{Ti(4)Mo(2)O(8)(OEt)(10)}(2)] (5). The single-crystal X-ray structures of the new cages 2, 3, 4, and 5 are reported. The results show that the size of the heterometallic cage formed can be influenced by the nuclearity of the precursor. In the case of 5, the presence of homometallic Mo-Mo bonding also appears to be a significant factor in the final structure.

Exchange of isonitrile ligands in the complex [Mo(O)Cl(CNMe)4]+ by the tetraphos ligand prP4: Stereochemical influences on the reaction course

Reaction of [Mo(O)Cl(CNMe)4]+ with the linear tetraphos ligand meso and rac prP4 leads to a mixture of [Mo(O)Cl(κ4-meso-prP4)]+ and [Mo(O)Cl(CNMe)(κ3-rac-prP4)]+ which are identified by X-ray structural analysis and/or 31P NMR spectroscopy. In the meso κ4-product both of the phenyl groups of the central phosphorus atoms are oriented towards the oxo ligand whereas in the rac κ3-product one of these phenyl groups is oriented to the oxo and the other to the chloro ligand. The origin of the different coordination modes lies in the different steric demands of the oxo and chloro ligands. The influences of the steric interactions are enhanced by the fact that exchange of the fourth isonitrile is difficult. This hypothesis is supported by the preparation of the complex [Mo(O)Cl(CNMe)(dpepp)]PF6 whose isonitrile ligand is inert towards exchange by monophosphines, even under drastic conditions.

Synthesis of all‐syn Functionalized Triphenylene Ketals

AbstractThe stereoselective synthesis of triphenylene ketals offers access to unique scaffolds. For a good performance in supramolecular applications an all‐syn orientation of the functional groups is essential. The oxidative trimerization of catechol ketals by molybdenum pentachloride or mixtures with titanium tetrachloride leads to a template‐directed formation. Several heterocyclic moieties are suitable for this transformation. A template‐directed isomerization of anti,anti,syn isomers to the desired C3‐symmetric derivative was demonstrated in two cases.

Synthesis and Characterization of the First Doubly‐bridged N,N‐dimethylthiocarbamoyl Metal Complex: Crystal Structure of [Mo(Cl)(CO)2(PPh3)]2(η1:η2:μ‐SCNMe2)2

AbstractThe first doubly‐bridged thiocarbamoyl metal complex [Mo(Cl)(CO)2(PPh3)]2(η1:η2:μ‐SCNMe2)2 (2) was formed from stirring [Mo(CO)2(η2‐SCNMe2)(PPh3)2Cl] (1) in dichloromethane at room temperature. Complex 2 is a dimer with each thiocarbamoyl unit coordinating through sulfur and carbon to one metal center and bridging both metals through sulfur. Complex 2 is characterized by X‐ray diffraction analysis.

Faster oxygen atom transfer catalysis with a tungsten dioxo complex than with its molybdenum analog

The synthesis and characterization of a series of molybdenum ([MoO(2)Cl(L(n))]; L(1) (1), L(2) (3)) and tungsten ([WO(2)Cl(L(n))]; L(1) (2), L(2) (4)) dioxo complexes (L(1) = 1-methyl-4-(2-hydroxybenzyl)-1,4-diazepane and L(2) = 1-methyl-4-(2-hydroxy-3,5-di-tert-butylbenzyl)-1,4-diazepane) of tridentate aminomonophenolate ligands HL(1) and HL(2) are reported. The ligands were obtained by reductive amination of 1-methyl-1,4-diazepane with the corresponding aldehyde. Complexes 3 and 4 were obtained by the reaction of [MO(2)Cl(2)(dme)(n)] (M = Mo, n = 0; W, n = 1) with the corresponding ligand in presence of a base, whereas for the preparation of 1 and 2 the ligands were deprotonated by KH prior to the addition to the metal. They were characterized by NMR and IR spectroscopy, by cyclic voltammetry, mass spectrometry, elemental analysis and by single-crystal X-ray diffraction analysis. Solid-state structures of the molybdenum and tungsten cis-dioxo complexes reveal hexa-coordinate metal centers surrounded by two oxo groups, a chloride ligand and by the tridentate monophenolate ligand which coordinates meridionally through its [ONN] donor set. In the series of compounds 1-4, complexes 3 and 4 have been used as catalysts for the oxygen atom transfer reaction between dimethyl sulfoxide (DMSO) and trimethyl phosphine (PMe(3)). Surprisingly, faster oxygen atom transfer (OAT) reactivity has been observed for the tungsten complex [WO(2)Cl(L(2))] (4) in comparison to its molybdenum analog [MoO(2)Cl(L(2))] (3) at room temperature. The kinetic results are discussed and compared in terms of their reactivity.