Molybdenum trioxide

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Molybdenum trioxide
Molybdan(VI)-oxid Kristallstruktur.png
Molybdenum trioxide powder.jpg
Names
IUPAC name
Molybdenum trioxide
Other names
Molybdic anhydride
Molybdite
Molybdic trioxide
Molybdenum(VI) oxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.823 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 215-204-7
PubChem CID
UNII
UN number 3288
  • InChI=1S/Mo.3O
    Key: JKQOBWVOAYFWKG-UHFFFAOYSA-N
  • O=[Mo](=O)=O
Properties
MoO3
Molar mass 143.95 g·mol−1
Appearanceyellow solid
Odor odorless
Density 4.70 g/cm3 [1]
Melting point 802 °C (1,476 °F; 1,075 K) [1]
Boiling point 1,155 °C (2,111 °F; 1,428 K)(sublimes) [1]
1.066 g/L (18 °C)
4.90 g/L (28 °C)
20.55 g/L (70 °C)
Band gap >3 eV (direct) [2]
+3.0·10−6 cm3/mol [3]
Structure [4]
Orthorhombic, oP16
Pnma, No. 62
a = 1.402 nm, b = 0.37028 nm, c = 0.39663 nm
4
see text
Thermochemistry [5]
75.0 J K−1 mol−1
Std molar
entropy (S⦵298)
77.7 J K−1 mol−1
−745.1 kJ/mol
-668.0 kJ/mol
Hazards [6]
GHS labelling:
GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg
Warning
H319, H335, H351
P201, P202, P261, P264, P271, P280, P281, P304+P340, P305+P351+P338, P308+P313, P312, P337+P313, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability (yellow): no hazard codeSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
0
OX
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
125 mg.kg (rat, oral)[ citation needed ]
2689 mg/kg (rat, oral) [7]
120 mg Mo/kg (rat, oral)
120 mg Mo/kg (guinea pig, oral) [7]
>5840 mg/m3 (rat, 4 hr) [7]
Related compounds
Other cations
Chromium trioxide
Tungsten trioxide
Molybdenum dioxide
"Molybdenum blue"
Related compounds
 Molybdic acid
Sodium molybdate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Molybdenum trioxide describes a family of inorganic compounds with the formula MoO3(H2O)n where n = 0, 1, 2. The anhydrous compound is produced on the largest scale of any molybdenum compound since it is the main intermediate produced when molybdenum ores are purified. The anhydrous oxide is a precursor to molybdenum metal, an important alloying agent. It is also an important industrial catalyst. [8] It is a yellow solid, although impure samples can appear blue or green.

Contents

Molybdenum trioxide occurs as the rare mineral molybdite.

Structure

A section of the chain comprising edge-sharing octahedra. Oxygen atoms in back and front of the chain link to other chains to build the layer. MoO3 chains.png
A section of the chain comprising edge-sharing octahedra. Oxygen atoms in back and front of the chain link to other chains to build the layer.

In the gas phase, three oxygen atoms are bonded to the central molybdenum atom. In the solid state, anhydrous MoO3 is composed of layers of distorted MoO6 octahedra in an orthorhombic crystal. The octahedra share edges and form chains which are cross-linked by oxygen atoms to form layers. The octahedra have one short molybdenum-oxygen bond to a non-bridging oxygen. [9] [10] Also known is a metastable (β) form of MoO3 with a WO3-like structure. [11] [2]

Preparation and principal reactions

Molybdite on molybdenite, Questa molybdenum mine, New Mexico (size: 11.0x6.7x4.1 cm). Molybdite-Molybdenite-233200.jpg
Molybdite on molybdenite, Questa molybdenum mine, New Mexico (size: 11.0×6.7×4.1 cm).

MoO3 is produced industrially by roasting the mineral molybdenite (molybdenum disulfide), the chief ore of molybdenum: [8]

2 MoS2 + 7 O2 → 2 MoO3 + 4 SO2

Similar procedures apply to the recovery of molybdenum from spent catalysts. The resulting trioxide can be purified by sublimation. The laboratory synthesis of the dihydrate entails acidification of aqueous solutions of sodium molybdate with perchloric acid: [12]

Na2MoO4 + H2O + 2 HClO4 → MoO3·2H2O + 2 NaClO4

The dihydrate loses water readily to give the monohydrate. Both are bright yellow in color. Molybdenum trioxide dissolves slightly in water to give "molybdic acid". In base, it dissolves to afford the molybdate anion.

Uses

Molybdenum trioxide is used to manufacture molybdenum metal:

MoO3 + 3 H2 → Mo + 3 H2O

Molybdenum trioxide is also a component of the co-catalyst used in the industrial production of acrylonitrile by the oxidation of propene and ammonia.

Because of its layered structure and the ease of the Mo(VI)/Mo(V) coupling, MoO3 is of interest in electrochemical devices and displays. It has been described as "the most commonly used TMO [transition metal oxide] in organic electronics applications ... it is evaporated at relatively low temperature (~400 °C)." [13] It has favourable electronic and chemical properties for use as interfacing layers, p-type dopants and hole transport materials in OLEDs, organic solar cells and perovskite solar cells, [14] especially when forming an ohmic contact to organic semiconductors. [15]

Related Research Articles

<span class="mw-page-title-main">Oxide</span> Chemical compound where oxygen atoms are combined with atoms of other elements

An oxide is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 that protects the foil from further oxidation.

An oxyanion, or oxoanion, is an ion with the generic formula A
xOz−
y. Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound H
zA
xO
y. The structures of condensed oxyanions can be rationalized in terms of AOn polyhedral units with sharing of corners or edges between polyhedra. The oxyanions adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are important in biology.

<span class="mw-page-title-main">Polyoxometalate</span> Polyatomic ion made of ≥3 transition metal oxyanions bound by oxygen in a 3D structure

In chemistry, a polyoxometalate is a polyatomic ion, usually an anion, that consists of three or more transition metal oxyanions linked together by shared oxygen atoms to form closed 3-dimensional frameworks. The metal atoms are usually group 6 or less commonly group 5 and group 7 transition metals in their high oxidation states. Polyoxometalates are often colorless, orange or red diamagnetic anions. Two broad families are recognized, isopolymetalates, composed of only one kind of metal and oxide, and heteropolymetalates, composed of one metal, oxide, and a main group oxyanion. Many exceptions to these general statements exist.

<span class="mw-page-title-main">Chromium trioxide</span> Chemical compound

Chromium trioxide is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions and bright orange when wet. The substance dissolves in water accompanied by hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser, a mutagen, and a carcinogen.

Selenic acid is the inorganic compound with the formula H2SeO4. It is an oxoacid of selenium, and its structure is more accurately described as O2Se(OH)2. It is a colorless compound. Although it has few uses, one of its salts, sodium selenate is used in the production of glass and animal feeds.

<span class="mw-page-title-main">Telluric acid</span> Chemical compound (Te(OH)6)

Telluric acid, or more accurately orthotelluric acid, is a chemical compound with the formula Te(OH)6, often written as H6TeO6. It is a white crystalline solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution. In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules, containing one hexavalent tellurium (Te) atom in the +6 oxidation state, attached to six hydroxyl (–OH) groups, thus, it can be called tellurium(VI) hydroxide. Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water. It is used as tellurium-source in the synthesis of oxidation catalysts.

<span class="mw-page-title-main">Molybdic acid</span> Chemical compound

Molybdic acid refers to hydrated forms of molybdenum trioxide and related species. The monohydrate (MoO3·H2O) and the dihydrate (MoO3·2H2O) are well characterized. They are yellow diamagnetic solids.

<span class="mw-page-title-main">Sodium molybdate</span> Chemical compound

Sodium molybdate, Na2MoO4, is useful as a source of molybdenum. This white, crystalline salt is often encountered as the dihydrate, Na2MoO4·2H2O.

Metal aromaticity or metalloaromaticity is the concept of aromaticity, found in many organic compounds, extended to metals and metal-containing compounds. The first experimental evidence for the existence of aromaticity in metals was found in aluminium cluster compounds of the type MAl−
4 where M stands for lithium, sodium or copper. These anions can be generated in a helium gas by laser vaporization of an aluminium / lithium carbonate composite or a copper or sodium / aluminium alloy, separated and selected by mass spectrometry and analyzed by photoelectron spectroscopy. The evidence for aromaticity in these compounds is based on several considerations. Computational chemistry shows that these aluminium clusters consist of a tetranuclear Al2−
4 plane and a counterion at the apex of a square pyramid. The Al2−
4 unit is perfectly planar and is not perturbed the presence of the counterion or even the presence of two counterions in the neutral compound M
2Al
4. In addition its HOMO is calculated to be a doubly occupied delocalized pi system making it obey Hückel's rule. Finally a match exists between the calculated values and the experimental photoelectron values for the energy required to remove the first 4 valence electrons. The first fully metal aromatic compound was a cyclogallane with a Ga32- core discovered by Gregory Robinson in 1995.

Potassium hypomanganate is the inorganic compound with the formula K3MnO4. Also known as potassium manganate(V), this bright blue solid is a rare example of a salt with the hypomanganate or manganate(V) anion, where the manganese atom is in the +5 oxidation state. It is an intermediate in the production of potassium permanganate and the industrially most important Mn(V) compound.

<span class="mw-page-title-main">Manganese heptoxide</span> Chemical compound

Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula Mn2O7. Manganese heptoxide is a volatile liquid with an oily consistency. It is a highly reactive and powerful oxidizer that reacts explosively with nearly any organic compound. It was first described in 1860. It is the acid anhydride of permanganic acid.

Technetium compounds are chemical compounds containing the chemical element technetium. Technetium can form multiple oxidation states, but often forms in the +4 and +7 oxidation states. Because technetium is radioactive, technetium compounds are extremely rare on Earth.

Rhenium trioxide or rhenium(VI) oxide is an inorganic compound with the formula ReO3. It is a red solid with a metallic lustre that resembles copper in appearance. It is the only stable trioxide of the Group 7 elements (Mn, Tc, Re).

<span class="mw-page-title-main">Molybdenum blue</span> Pigment

Molybdenum blue is a term applied to:

<span class="mw-page-title-main">Dichlorine hexoxide</span> Chemical compound

Dichlorine hexoxide is the chemical compound with the molecular formula Cl
2O
6, which is correct for its gaseous state. However, in liquid or solid form, this chlorine oxide ionizes into the dark red ionic compound chloryl perchlorate [ClO
2]+
[ClO
4]−
, which may be thought of as the mixed anhydride of chloric and perchloric acids.

<span class="mw-page-title-main">Molybdate</span> Chemical compound of the form –O–MoO₂–O–

In chemistry, a molybdate is a compound containing an oxyanion with molybdenum in its highest oxidation state of 6: O−−Mo(=O)2−O−. Molybdenum can form a very large range of such oxyanions, which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state. The larger oxyanions are members of group of compounds termed polyoxometalates, and because they contain only one type of metal atom are often called isopolymetalates. The discrete molybdenum oxyanions range in size from the simplest MoO2−
4, found in potassium molybdate up to extremely large structures found in isopoly-molybdenum blues that contain for example 154 Mo atoms. The behaviour of molybdenum is different from the other elements in group 6. Chromium only forms the chromates, CrO2−
4, Cr
2O2−
7, Cr
3O2−
10 and Cr
4O2−
13 ions which are all based on tetrahedral chromium. Tungsten is similar to molybdenum and forms many tungstates containing 6 coordinate tungsten.

<span class="mw-page-title-main">Chromyl fluoride</span> Chemical compound

Chromyl fluoride is an inorganic compound with the formula CrO2F2. It is a violet-red colored crystalline solid that melts to an orange-red liquid.

<span class="mw-page-title-main">Manganese(II) molybdate</span> Inorganic compound

Manganese(II) molybdate is an inorganic compound with the chemical formula MnMoO4. α-MnMoO4 has a monoclinic crystal structure. It is also antiferromagnetic at low temperatures.

Ammonium dimolybdate (ADM) is the inorganic compound with the formula (NH4)2Mo2O7. It is a white, water-soluble solid. ADM is an intermediate in the production of molybdenum compounds from its ores. Roasting typical ore produces crude molybdenum(VI) oxides, which can be extracted into aqueous ammonia, affording ammonium molybdate. Heating solutions of ammonium molybdate gives ADM. Upon heating, solid ammonium dimolybdate decomposes to molybdenum trioxide:

Rhenium compounds are compounds formed by the transition metal rhenium (Re). Rhenium can form in many oxidation states, and compounds are known for every oxidation state from -3 to +7 except -2, although the oxidation states +7, +4, and +3 are the most common. Rhenium is most available commercially as salts of perrhenate, including sodium and ammonium perrhenates. These are white, water-soluble compounds. The tetrathioperrhenate anion [ReS4]− is possible.

References

  1. 1 2 3 Haynes, p. 4.77
  2. 1 2 Balendhran, Sivacarendran; Walia, Sumeet; Nili, Hussein; Ou, Jian Zhen; Zhuiykov, Serge; Kaner, Richard B.; Sriram, Sharath; Bhaskaran, Madhu; Kalantar-zadeh, Kourosh (2013-08-26). "Two-Dimensional Molybdenum Trioxide and Dichalcogenides". Advanced Functional Materials. 23 (32): 3952–3970. doi:10.1002/adfm.201300125. S2CID   95301280.
  3. ↑ Haynes, p. 4.134
  4. ↑ Åsbrink, S.; Kihlborg, L.; Malinowski, M. (1988). "High-pressure single-crystal X-ray diffraction studies of MoO3. I. Lattice parameters up to 7.4 GPa". J. Appl. Crystallogr. 21 (6): 960–962. doi:10.1107/S0021889888008271.
  5. ↑ Haynes, p. 5.15
  6. ↑ "Molybdenum trioxide". PubChem.
  7. 1 2 3 "Molybdenum (soluble compounds, as Mo)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  8. 1 2 Roger F. Sebenik; et al. (2005). "Molybdenum and Molybdenum Compounds". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_655. ISBN   978-3527306732.
  9. 1 2 "Molybdite Mineral Data". Webmineral.
  10. ↑ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN   0-19-855370-6.
  11. ↑ McCarron, E. M. (1986). "β-MoO3: A Metastable Analogue of WO3". J. Chem. Soc., Chem. Commun. (4): 336–338. doi:10.1039/C39860000336.
  12. ↑ Heynes, J. B. B.; Cruywagen, J. J. (1986). "Yellow Molybdenum(VI) Oxide Dihydrate". Inorganic Syntheses. Vol. 24. pp. 191–2. doi:10.1002/9780470132555.ch56. ISBN   9780470132555.
  13. ↑ Meyer, Jens; Hamwi, Sami; Kröger, Michael; Kowalsky, Wolfgang; Riedl, Thomas; Kahn, Antoine (2012). "Transition Metal Oxides for Organic Electronics: Energetics, Device Physics and Applications". Advanced Materials. 24 (40): 5408–5427. Bibcode:2012AdM....24.5408M. doi:10.1002/adma.201201630. PMID   22945550. S2CID   197055498.
  14. ↑ White, Robin T.; Thibau, Emmanuel S.; Lu, Zheng-Hong (2016-02-16). "Interface Structure of MoO3 on Organic Semiconductors". Scientific Reports. 6 (1): 21109. Bibcode:2016NatSR...621109W. doi:10.1038/srep21109. ISSN   2045-2322. PMC   4754744 . PMID   26880185.
  15. ↑ Gong, Yongshuai; Dong, Yiman; Zhao, Biao; Yu, Runnan; Hu, Siqian; Tan, Zhan'ao (2020). "Diverse applications of MoO 3 for high performance organic photovoltaics: fundamentals, processes and optimization strategies". Journal of Materials Chemistry A. 8 (3): 978–1009. doi:10.1039/C9TA12005J. ISSN   2050-7488. S2CID   213237371.

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