Molybdenum-oxygen Bonds Research Articles

Enabling deep conversion reactions by weakening molybdenum-oxygen bonds through K+ pre-intercalation

Conversion-type transition metal oxides (TMOs) anodes with fascinating high theoretical capacities are considered potential candidates for high-energy-density alkali-ion batteries. However, the tremendous advantages of conversion reaction are yet to be fully exploited due to sluggish reaction kinetics and unfavorable thermodynamics. This is especially in the case of non-layered TMOs, where high ion intercalation energy and ion diffusion barriers compared to layered TMOs impede subsequent conversion reaction, while thermodynamically stable metal-oxide bonds with high bond energies prevent efficient cleavage. This work selects MoO2 as a typical non-layered anode of lithium-ion batteries and demonstrates that pre-intercalating K+ ions in MoO2 crystal can decrease the intercalation energy, enhance the diffusion kinetics, and weaken Mo-O bonds to efficiently facilitate conversion reactions by the the density functional theory calculations and experiments. K+ pre-intercalated MoO2 can deliver a higher reversible discharge specific capacity (989 mAh g−1) than the pristine MoO2 sample (720 mAh g−1) at 0.2 A g−1 after 100 cycles. This work provides a novel and crucial method to realize the functionality of non-layered TMOs based anodes and offers a potentially universal optimization strategy toward high-capacity alkali-ion batteries.

Effects of Yb3+ ion doping on lattice distortion, optical absorption and light upconversion in Er3+/Yb3+ co-doped SrMoO4 ceramics

Sintered ceramic pellets of rare-earth ion doped strontium molybdate compositions Sr1-x-yErxYbyMoO4 (x = 1 mol%; y = 0–9 mol%) were prepared using solid-state reaction method. Rietveld refinement of HR-XRD data reveals a high degree of lattice distortion for y = 3 mol %, and correspondingly a maximum deviation in the O–Sr–O and Mo–O bonds. Raman spectroscopy indicates the substitution of Er3+ and Yb3+ at the SrO8 polyhedron clusters of the SrMoO4 unit cell, and infrared absorption shows changes in the molybdenum-oxygen (Mo–O) bond strength in the [MoO4]2⎻ cluster. Variations in the optical band gap are attributed to positional change of oxygen octahedra and local bond distortion in the unit cell. A selective enhancement in green up-conversion luminescence is seen at y = 3 mol %, and originates due to direct contribution from the [Yb3+⎼MoO4]2- dimer complex sensitization, and correlates with the presence of high lattice distortion. A progressive increase in lifetime of the 4S3/2 from 0.195 to 0.424 ms at y = 0.03 increase the radiative transition probability and UC emission. Luminescence quenching for Yb3+ ion content (y > 0.03) is due to the reduced asymmetrical arrangement around erbium ion and corresponding changes in the Sr–O and Mo–O bond lengths. These studies provide new insight into the quenching effect and formulate a new strategy to design ceramic compositions for better UC performance.

Padding molybdenum net with Graphite/MoO3 composite as a multi-functional interlayer enabling high-performance lithium-sulfur batteries

The development of “beyond lithium-ion” battery systems with high energy density are urgently required due to the increasing demand for electric vehicles and compact energy storage applications. LithiumSulfur batteries are considered as the most promising candidate owing to their high energy and low cost. However, shuttle effect of lithium polysulfide between the cathode and anode is one of the vital obstacles limiting their commercial application. Here, we design and fabricate a multi-functional interlayer by padding the molybdenum net with graphite or graphite/molybdenum trioxide composite that is able to adsorb polysulfide effectively thus alleviate the diffusion of polysulfide. The weak molybdenum-oxygen bonds on the surface of molybdenum trioxide nanoparticles provide efficient adsorption site to capture polysulfide. In addition, part of molybdenum trioxide can have lithium-ion intercalated to form lithium molybdenum trioxide, which contributes extra reversible capacity for the lithium-sulfur battery. molybdenum net ensures high electron conductivity and mechanical flexibility to facilitate charge transfer and endure inner stress. Coupling these advantages together, the lithium-sulfur cells with the multi-functional interlayer achieve a reversible capacity of 816 mAh g−1 after 500 cycles with the capacity retention of 95%.

Computational Study of Solvent Effects and the Vibrational Spectra of Anderson Polyoxometalates

The structures and vibrational frequencies of the type II Anderson heteropolyanions [TeMo6O24]6- and [IMo6O24]5- have been calculated by using density functional theory using a number of common functionals and basis sets. For the first time, Raman intensities have been calculated and the effect of solvent on the modeling has been investigated. The calculated IR and Raman spectral traces are in good agreement with experiment allowing the characteristic group frequencies for this class of polyoxometalate to be identified. The stretching vibrations of the molybdenum-oxygen bonds are predicted to occur at somewhat lower frequencies than in the type I polyoxometalates. Stretching of the heteroatom-oxygen bonds occurs at significantly lower frequencies than in the Keggin anions as a simple consequence of the higher coordination number of the central heteroatom in the Anderson systems. For the [Mo2O7]2- and [Mo6O19]2- ions, the relatively low negative charge leads to small structural changes when solvent is included. In these systems, solvent leads to an increase in the bond polarity and a decrease in the covalent bond orders, resulting in decreases in the calculated frequencies. For the Anderson anions, the higher negative charges leads to greater solvent effects with contraction of the clusters and increases in the frequencies of bands due to stretching of the two, cis-related molybdenum-oxygen bonds.

New iso and heteropolyoxomolybdates: synthesis and molecular structure of the anions [Mo VI 8O 26(OH)] 5−, [HAs IIIAs VMo VMo VI 8O 34] 6− and [HAs IIIAs VMo VMo VI 8O 34{Co(C 5H 5N) 2(H 2O) 3}] 4−

The hydrothermal reaction of Na 2MoO 4 with pyridine in water at pH 5 and 130 °C gives the octamolybdate anion [Mo VI 8O 26(OH)] 5− ( 1) which crystallises as the pyridinium salt; its molecular structure derives from that of the parent α-octamolybdate anion [Mo VI 8O 26] 4− by opening two molybdenumoxygen bond and adding a hydroxo bridge. The same reaction in the presence of NaAsO 2 yields the mixed-valence arsenatomolybdate [Has IIIAs VMo VMo VI 8O 34] 6− ( 2) which is also isolated as the pyridinium salt. Anion 2 has a lacunary structure like an open basket, which derives from the famous α-Keggin structure by removing three edge-sharing MoO 6 octahedra and by capping a trioxygen face of three remaning MoO 6 octahedra with an AsH group. Reaction of 2 with Co 2+ leads to the anion [HAs IIIAs VMo VMo VI 8O 34{Co(C 5H 5N) 2(H 2O) 3}] 4− ( 3) which crystallises as a double pyridinium salt together with anion 2. The structure of 3 derives from that of 2 by attaching a Co(C 5H 5N) 2(H 2O) 3 fragment to a terminal oxo ligand. Reaction of 2 with hydrogen peroxide produces the fully oxydised α-Keggin anion [As VMo VI 12O 40] 3− ( 4) which was found to crystallise as the tetrabutylammonium salt surprisingly with three independent molecules in the unit cell, two of them showing a remarkable disorder.

Photochemistry of molybdenum(V) tetraphenylporphyrin studied by laser flash photolysis: light-induced homolysis of the molybdenum-oxygen bond of oxoalkoxo- and oxo(nitrito)molybdenum(V) tetraphenylporphyrin

Photochemistry of molybdenum(V) tetraphenylporphyrin studied by laser flash photolysis: light-induced homolysis of the molybdenum-oxygen bond of oxoalkoxo- and oxo(nitrito)molybdenum(V) tetraphenylporphyrin

Crystal and molecular structure of ?-oxobis[bis(dipropyl dithiophosphato) oxomolybdenum(V)

The title compound is triclinic, space group P¯1,a=10.670(5)b=13.053(3),c=8.944(5) A,α=100.18(3),β=92.16(4),γ=80.88(3)°,Z=1,V=1210.4 A3, andR=0.043 for 2579 reflections. The molecule has two distorted octahedra sharing a corner occupied by an oxygen (bridging) atom, the Mo-Ob-Mo angle being 180°. The two molybdenum-oxygen bond lengths Mo-Ob (bridging) and Mo-O1, (terminal) are 1.92 and 1.62 A, respectively. Except the Mo-S bondtrans to the terminal oxygen atom which has a bond length 2.81 A, all other Mo-S bonds have an average length of 2.50 A.

Determination of molybdenum–oxygen bond distances and bond orders by Raman spectroscopy

AbstractA correlation is developed for relating Raman stretching frequencies of molybdenum–oxygen (MoO) bonds to their respective bond distances in molybdenum oxide compounds. MoO bond orders are also related to stretching frequencies. The MoO correlation is expected to offer invaluable insight into the structures of molybdate species in chemical systems which are not amenable to analysis by diffraction or other spectroscopic techniques. In the present study, the correlation is used to predict stretching frequencies for perfect MoO4 and MoO6 structures, and to determine MoO bond distances of the MoO6 octahedron in Ba2CaMoO6 as well as the dehydrated surface molybdate species in MoO3/Al2O3.

Carbomolybdate clusters formed by carbonyl insertion into molybdenum-oxygen bonds. Structural investigation of the [RMo 4O 15X] 3− core (R  C 9H 4O, X  OCH 3; R  C 14H 10, X  C 7H 5O 2; R  C 14H 8, X  OH)

[C 4H 9) 4N] 2[Mo 2O 7] reacts with a variety of organic species containing α-diketone groups to give tetranuclear complexes of general composition [RMo 4O 15X] 3−. The complexes [(C 4H 9) 4N] 3[(C 9H 4O)Mo 4O 15(OCH 3)] ( I), [(C 4H 9) 4N] 3[(C 14H 10)Mo 4O 15(C 6H 5CO 2)] ( 11) and [(C 4H 9) 4N] 3[(C 14H 8)Mo 4O 15(OH)] ( III) were synthesized from the reactions of dimolybdate with ninhydrin, benzil and phenanthraquinone, respectively. Complex II may also be prepared from dimolybdate and benzoin in acetonitrile-methanol solution, from which it co-crystallizes with the binuclear species [(C 4H 9) 4N] 2[Mo 2O 5(C 6H 5C(O)C(O)C 6H 5) 2] · CH 3CN · CH 3OH ( IV). Complexes I–III exhibit the tetranuclear core, previously described for the α-glyoxal derivatives [(C 4H 9) 4N] 3[(HCCH)Mo 4O 15X], where X  F − or HCO 2 −. The ligands may be formally described as diketals, formed by insertion of ligand carbonyl subunits into molybdenum-oxygen bonds. The structures I–III differ most dramatically in the identity and coordination mode of the anionic ligand X − which occupies a position opposite the diketal moiety relative to the [Mo 4O 11] 2+ central cage. Thus, I exhibits a doubly bridging methoxy group in this position, while II possesses a benzoate ligand with an unusual μ 3-O,O′coordination mode. Complex III presents a hydroxy-group unsymmetrically bonded to three of the molybdenum centres. The stereochemical consequences of the various coordination modes are discussed. Crystal data: Compound I, monoclinic space group Pc, a = 24.888(2), b = 12.897(3), c = 24.900(3) Å, β = 101.94(2)°, D calc = 1.28 g cm −1 for Z = 4. Structure solution and refinement based on 8695 reflections with F o ⩾ 6σ(F o) (Mo- K α , λ = 0.71073 Å) converged at a conventional discrepancy factor of 0.060. Compound II, orthorhombic space group Pbca, a = 20.426(6), b = 26.916(6), c = 32.147(7) Å, V = 17673.2(20) Å 3, D calc = 1.33 g cm −3 for Z = 8; 5224 reflections, R = 0.076. Compound III, tetragonal space group I4 1/ a, a = b = 48.129(6), c = 13.057(2) Å, V = 30246.2(12) Å 3, D calc = 1.35 g cm −3 for Z = 16; 5554 reflections, R = 0.053. Compound IV, orthorhombic space group Pnca, a = 16.097(4), b = 16.755(4), c = 25.986(7) Å, V = 7008.1(13) Å 3, Z = 4, D calc = 1.18 g cm −3 ; 2944 reflections, R = 0.061.

Reactions of the metallabromoalkane [Mo{(CH2)3Br}(CO)3(η-C5H5)] and the carbene complexes trans-[MoI{C(CH2)3O}(CO)2(η-C5H4R)](R = H or Me) with Li(BEt3H). The synthesis (R = H or Me) and X-ray structure (R = Me) of [Mo{CH(CH2)3O}(CO)2(η-C5H4R)] containing an unusual oxygen–molybdenum donor interaction

The reaction of [Mo{(CH2)3Br}(CO)3(η-C5H5)] with Li(BEt3H) leads to the spectroscopically characterised [[graphic omitted]}(CO)2(η-C5H5)]. This compound is also formed in the reaction of the carbene complex trans-[MoI{[graphic omitted]}(CO)2(η-C5H5)] with Li(BEt3H). In both reactions small quantities of the known η3-ally[Mo(CO)2(η3-C4H7)(η-C5H5)] are also isolated. The methylcyclopentadienyl analogues are available through reaction of trans-[MoI{[graphic omitted]}(CO)2(η-C5H4Me)] with Li(BEt3H) and the resulting molecule [[graphic omitted]}(CO)2(η-C5H4Me)] is the subject of an X-ray crystal structure determination. It crystallises as irregular red lumps, a= 8.416(9), b= 11.541(12), c= 7.063(3)Å, α= 105.23(3), β= 105.71(3), and γ= 104.938(12)°; R converged to 0.0299 for 1 805 independent reflections for which I > 3.0 σ(I). The bonding of the C4H7O ring is unusual and formulated as a metal–alkyl interaction adjacent to a O → Mo bond. The molybdenum–oxygen bond is labile, thus [[graphic omitted]}(CO)2(η-C5H5)] reacts readily with PPh3 to give the phosphine complex trans-[Mo{[graphic omitted]}(CO)2(PPh3)(η-C5H5)] in good yield. Formation of [[graphic omitted]}(CO)2(η-C5H5)] from the alkyl complex proceeds by the initial formation of a metal formyl complex [Mo(CHO){(CH2)3Br}(CO)2(η-C5H5)]– which rearranges through two further intermediates to the ultimate product. Formation of [[graphic omitted]}(CO)2(η-C5H4R)] from the appropriate carbene complex is apparently by direct attack of the hydride reagent at the carbene atom. Reaction of the alkyl trans-[Mo{(CH2)3Br}(CO)2(PPh3)(η-C5H5)] with Li(BEt3H) leads only to the η3-allyl [Mo(CO)(PPh3)(η3-C4H7)(η-C5H5)].

12-heteropolymolybdates as catalysts for vapor-phase oxidative dehydrogenation of isobutyric acid: I. Alkali and alkaline-earth metal salts

The effects of cations and heteroatoms on the catalytic activity and selectivity of 12-heteropolymolybdates, as catalysts, have been investigated in the vapor-phase oxidative dehydrogenation of isobutyric acid. The conversion of isobutyric acid at 300 °C increased with decreasing electronegativity of the cations (H +, alkali, and alkaline-earth metal ions) and the heteroatoms (P 5+, As 5+, and Si 4+), whereas it decreased with the change in the nature of the cations at 250 °C. The yield ratio (acetone/methacrylic acid) at 300 °C showed a behavior similar to the conversion, but the ratio was maximum over lithium and strontium salts. On the other hand, the electron affinity of Mo 6+ in these 12-heteropolymolybdate-type catalysts paralleled the electronegativity of the cations and the heteroatoms, and the reactivity of Mo 5+ to gaseous oxygen increased with decreasing electronegativity of these catalyst components (cations and heteroatoms). These results are discussed as the effects of these catalyst components on the electrochemical properties of the molybdenum atom, and the catalytic results obtained are explained on the basis of the exclusive participation of the lattice oxygen, the strength of molybdenum-oxygen bond, and the acid-base properties of the catalyst. It is shown that the molybdenum-oxygen bond is weakened as the catalyst components become less electronegative.

ChemInform Abstract: OXYGEN‐17 NUCLEAR MAGNETIC RESONANCE SPECTRA OF CERTAIN OXOMOLYBDENUM(VI) COMPLEXES AND THE INFLUENCE OF THE MULTIPLICITY OF THE MOLYBDENUM‐OXYGEN BOND

Chemischer InformationsdienstVolume 10, Issue 29 Physical Organic Chemistry ChemInform Abstract: OXYGEN-17 NUCLEAR MAGNETIC RESONANCE SPECTRA OF CERTAIN OXOMOLYBDENUM(VI) COMPLEXES AND THE INFLUENCE OF THE MULTIPLICITY OF THE MOLYBDENUM-OXYGEN BOND K. F. MILLER, K. F. MILLERSearch for more papers by this authorR. A. D. WENTWORTH, R. A. D. WENTWORTHSearch for more papers by this author K. F. MILLER, K. F. MILLERSearch for more papers by this authorR. A. D. WENTWORTH, R. A. D. WENTWORTHSearch for more papers by this author First published: July 17, 1979 https://doi.org/10.1002/chin.197929049Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue29July 17, 1979 RelatedInformation

Oxygen-17 nuclear magnetic resonance spectra of certain oxomolybdenum(VI) complexes and the influence of the multiplicity of the molybdenum-oxygen bond

Oxygen-17 nuclear magnetic resonance spectra of certain oxomolybdenum(VI) complexes and the influence of the multiplicity of the molybdenum-oxygen bond

The chemistry of molybdenum and tungsten. Part XIII. Molybdenum(V) complexes of dithiocarbamates and dithioethers

Oxotrichloromolybdenum(V) reacts with dithiocarbamates. R 2dtc − (R 2  Me 2, Et 2, [CH 2] 4) in acetonitrile at room temperature with cleavage of the terminal molybdenum-oxygen bond to yield [Mo(R 2dtc) 4] +, isolated as the chloride or tetraphenylborate salts; infrared spectra indicate bidentate coordination by the ligands, and these complexes appear to have dodecahedral geometry. From this same reaction can be isolated the dimeric [Mo 2O 4(R 2dtc) 2] species which contain a double MoOMo bridges as well as terminal MoO bonds, and also the [Mo 2O 3(Et 2dtc)] complex containing a single MoOMo bridge and two terminal MoO linkages. With a series of dithioethers oxotrichloromolybdenum(V) yields [MoO(ligand)Cl 3], but the ability to complex depends critically on the structure of the dithioether. The structures of these complexes have been assigned with the aid of vibrational, electronic and electron paramagnetic resonance spectroscopy.

Thermochemical studies of molybdenum dithio-carbamate complexes as models for molybdoenzymes

Calorimetric measures for interconverting the oxidation states (IV), (V) and (VI) in dithiocarbamato complexes of molybdenum with accompanying oxo group transfer were carried out in 1,2-dichloroethane at 25 °C. Supplementary ΔH data for known substrates of molybdoenzymes were also measured. Combinations of these data yielded thermochemical results for hypothetical reactions between biological substrates and the oxidation states (IV), (V) and (VI) of molybdenum in these dithiocarbamato model compounds. Bond energies for terminal and bridging molybdenum-oxygen bonds in these complexes were calculated to be +96 and +101 kcal mol −1, respectively.

The K 4Mo 2Cl 8-NOCl, Mo 2(C 2H 3O 2) 4-NOCl, and [(C 2H 5)N] 3Mo 2Cl 9-NOCl systems in ethyl acetate

The behavior of the K 4Mo 2Cl 8-NOCl, Mo 2(C 2H 3O 2) 4-NOCl, and [(C 2H 5)N] 3Mo 2Cl 9-NOCl systems in ethyl acetate has been investigated. In every case, only products were found in which the molybdenum-molybdenum multiple bonds of the starting complexes had been cleaved. After appropriate work-up of the K 4Mo 2Cl 8-NOCl system immediately after reaction, the complexes K 2Mo(NO)Cl 5 and Mo(NO)Cl(in3)·2(C 6H 5) 3PO were isolated. Infrared evidence indicated that these compounds were contaminated with species containing molybdenum-oxygen bonds, and indeed, extended reaction times resulted in marked decreases in the relative intensity of the absorption characteristics of NO stretch and increases in the intensities of those absorptions attributable to molybdenum-oxygen linkages. Reaction of NOCl with Mo 2(C 2H 3O 2) 4 gave, after treatment of the ethyl acetate solution with triphenylphosphine oxide, practically quantitative yields of Mo(NO)Cl(in3)·2(C 6H 5) 3PO. Again, the compound was apparently contaminated with substances having molybdenum-oxygen bonds. It is worth noting that the initial reactions of NOCl with K 4Mo 2Cl 8 and Mo 2(C 2H 3O 2) 4 occurred with little oxidation of the dipositive molybdenum. The major products obtained after work-up of the [(C 2H 5) 4N]Mo 2Cl 9-NOCl system were [(C 2H 5) 4N] 2Mo(NO)Cl 5, [(C 2H 5) 4N] −MoCl 4(H 2O) x (x = 1−2), and MoO 2Cl 2·2(C 6H 5) 3PO. It is proposed that [(C 2H 5) 4N] 2Mo(NO)Cl 5 is formed by reaction of a molybdenum(III) species with NO, the latter arising from the reduction of NOCl.

Interaction of molybdenum (V) oxotrichloride with certain aliphatic amines

1. The interaction of MoOCl3 with monoethyl-, dimethyl-, diethyl-, trimethyl-, and triethylamines was studied. 2. The reactions of MoOCl3 with primary and secondary alkylamines are accompanied by solvolysis at the molybdenum-chlorine bonds. Compounds with the composition MoOCl2NHC2H5; MoOCl2N(CH3)2; MoOCl[N(C2H5)2]2. were isolated. 3. As a result of the interaction of MoOCl3 with trimethyl- and triethylamines, compounds with the composition: MoOCl3·N(CH3)3 and MoOCl3·N(C2H5)3, respectively, are formed. 4. According to the IR spectra, the molybdenum-oxygen bonds in the compounds represent a ⋯Mo··OMoOMoO⋯ chain of increased multiplicity. 5. As a result of pyrolysis under vacuum or an inert atmosphere at 500–600°C, all the compounds isolated decompose to molybdenum dioxide.

Spectroscopic investigation of bismuth–molybdenum–oxide catalysts

Bismuth–molybdenum–oxide catalysts have been studied by i.r. and u.v. reflectance spectroscopy. Both tetrahedral and octahedral oxomolybdenum(VI) species were at the catalyst surface. The proportion of octahedral species increased with increasing molybdenum concentration and with increasing calcining temperature. The i.r. spectra showed the presence at the surface of an octahedral oxomolybdenum(VI) species with terminal and bridging oxygen. The most active catalysts, including silica-supported catalysts, had characteristic u.v. and i.r. spectra. Molybdenum–terminal oxygen stretching frequencies were in the range found in model compounds with three terminal oxygens per molybdenum. The effect of silica in supported catalysts was to promote formation of the same active species as in the unsupported catalyst but at a higher molybdenum concentration. The relevance of our results to the mechanism of the catalysis of oxidative dehydrogenation of olefines is discussed. We suggest that the bifunctional nature of the bismuth molybdate catalyst is due to the presence of two types of molybdenum–oxygen bond in the particular structure adopted by MoO3 in association with Bi2O3.