:Molybdenum trioxide
{{chembox
|Verifiedfields=changed
|Watchedfields=changed
|verifiedrevid=431943482
|ImageFileL1=Molybdän(VI)-oxid Kristallstruktur.png
|ImageName=Molybdenum trioxide
|ImageFileR1=Molybdenum trioxide powder.jpg
|IUPACName=Molybdenum trioxide
|OtherNames=Molybdic anhydride
Molybdite
Molybdic trioxide
Molybdenum(VI) oxide
|Section1={{Chembox Identifiers
| CASNo = 1313-27-5
| CASNo_Comment = anhydrous
| CASNo_Ref = {{cascite|correct|CAS}}
| ChEBI = 30627
| ChemSpiderID = 14118
| EC_number = 215-204-7
| PubChem = 14802
| UNNumber = 3288
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 22FQ3F03YS
| StdInChI=1S/Mo.3O
| StdInChIKey = JKQOBWVOAYFWKG-UHFFFAOYSA-N
| SMILES = O=[Mo](=O)=O
}}
|Section2={{Chembox Properties
| Mo=1 | O=3
| Appearance = yellow solid
| Odor = odorless
| Density = 4.70 g/cm3Haynes, p. 4.77
| Solubility = 1.066 g/L (18 °C)
4.90 g/L (28 °C)
20.55 g/L (70 °C)
| MeltingPtC = 802
| BoilingPtC = 1155
| BandGap = >3 eV (direct){{Cite journal|last1=Balendhran|first1=Sivacarendran|last2=Walia|first2=Sumeet|last3=Nili|first3=Hussein|last4=Ou|first4=Jian Zhen|last5=Zhuiykov|first5=Serge|last6=Kaner|first6=Richard B.|last7=Sriram|first7=Sharath|last8=Bhaskaran|first8=Madhu|last9=Kalantar-zadeh|first9=Kourosh|date=2013-08-26|title=Two-Dimensional Molybdenum Trioxide and Dichalcogenides|journal=Advanced Functional Materials|volume=23|issue=32|pages=3952–3970|doi=10.1002/adfm.201300125|s2cid=95301280 }}
| pKa =
| MagSus = +3.0·10−6 cm3/molHaynes, p. 4.134
}}
|Section3={{Chembox Structure
| Coordination = see text
| CrystalStruct = Orthorhombic, oP16
| SpaceGroup = Pnma, No. 62
| LattConst_a = 1.402 nm
| LattConst_b = 0.37028 nm
| LattConst_c = 0.39663 nm
| LattConst_alpha =
| LattConst_beta =
| LattConst_gamma =
| LattConst_ref =
| LattConst_Comment =
| UnitCellVolume =
| UnitCellFormulas = 4
}}
|Section4={{Chembox Thermochemistry
| Thermochemistry_ref =Haynes, p. 5.15
| DeltaHf = −745.1 kJ/mol
| Entropy = 77.7 J K−1 mol−1
| HeatCapacity = 75.0 J K−1 mol−1
| DeltaGfree = −668.0 kJ/mol
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS07}}{{GHS08}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|319|335|351}}
| PPhrases = {{P-phrases|201|202|261|264|271|280|281|304+340|305+351+338|308+313|312|337+313|403+233|405|501}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R =
| NFPA-S = OX
| FlashPt = Non-flammable
| LD50 = 125 mg.kg (rat, oral){{citation needed|date=July 2015}}
2689 mg/kg (rat, oral)
| LC50 = >5840 mg/m3 (rat, 4 hr){{IDLH|moly-mo|Molybdenum (soluble compounds, as Mo)}}
| LDLo = 120 mg Mo/kg (rat, oral)
120 mg Mo/kg (guinea pig, oral)
}}
|Section8={{Chembox Related
| OtherAnions =
| OtherCations = Chromium trioxide
Tungsten trioxide
| OtherFunction = Molybdenum dioxide
"Molybdenum blue"
| OtherFunction_label = molybdenum oxides
| OtherCompounds = Molybdic acid
Sodium molybdate
}}
}}
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.{{Ullmann|author=Roger F. Sebenik|display-authors=etal|title=Molybdenum and Molybdenum Compounds|year=2005|doi=10.1002/14356007.a16_655|isbn=978-3527306732}} It is a yellow solid, although impure samples can appear blue or green.
Structure
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.{{Cite web|url=http://www.webmineral.com/data/Molybdite.shtml|title=Molybdite Mineral Data|website=Webmineral}}Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. {{ISBN|0-19-855370-6}}. Also known is a metastable (β) form of MoO3 with a WO3-like structure.{{Cite journal|last=McCarron|first=E. M.|date=1986|title=β-MoO3: A Metastable Analogue of WO3|journal=J. Chem. Soc., Chem. Commun.|issue=4|pages=336–338|doi=10.1039/C39860000336}}
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Preparation and principal reactions
File:Molybdite-Molybdenite-233200.jpg, Questa molybdenum mine, New Mexico (size: 11.0×6.7×4.1 cm).|left]]
MoO3 is produced industrially by roasting the mineral molybdenite (molybdenum disulfide), the chief ore of molybdenum:
: {{chem2|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:{{cite book|doi=10.1002/9780470132555.ch56|author1=Heynes, J. B. B. |author2=Cruywagen, J. J. |title=Inorganic Syntheses |chapter=Yellow Molybdenum(VI) Oxide Dihydrate |year= 1986| volume =24|pages=191–2|isbn=9780470132555 }}
:{{chem2|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)."{{cite journal |doi=10.1002/adma.201201630|title=Transition Metal Oxides for Organic Electronics: Energetics, Device Physics and Applications |year=2012 |last1=Meyer |first1=Jens |last2=Hamwi |first2=Sami |last3=Kröger |first3=Michael |last4=Kowalsky |first4=Wolfgang |last5=Riedl |first5=Thomas |last6=Kahn |first6=Antoine |journal=Advanced Materials |volume=24 |issue=40 |pages=5408–5427 |pmid=22945550 |bibcode=2012AdM....24.5408M |s2cid=197055498 }} 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,{{Cite journal |last1=White |first1=Robin T. |last2=Thibau |first2=Emmanuel S. |last3=Lu |first3=Zheng-Hong |date=2016-02-16 |title=Interface Structure of MoO3 on Organic Semiconductors |journal=Scientific Reports |language=en |volume=6 |issue=1 |pages=21109 |doi=10.1038/srep21109 |issn=2045-2322 |pmc=4754744 |pmid=26880185|bibcode=2016NatSR...621109W }} especially when forming an ohmic contact to organic semiconductors.{{Cite journal |last1=Gong |first1=Yongshuai |last2=Dong |first2=Yiman |last3=Zhao |first3=Biao |last4=Yu |first4=Runnan |last5=Hu |first5=Siqian |last6=Tan |first6=Zhan'ao |date=2020 |title=Diverse applications of MoO 3 for high performance organic photovoltaics: fundamentals, processes and optimization strategies |url=http://xlink.rsc.org/?DOI=C9TA12005J |journal=Journal of Materials Chemistry A |language=en |volume=8 |issue=3 |pages=978–1009 |doi=10.1039/C9TA12005J |s2cid=213237371 |issn=2050-7488|url-access=subscription }}
References
{{reflist}}
Cited sources
- {{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = CRC Press | isbn = 978-1439855119| title-link = CRC Handbook of Chemistry and Physics }}
External links
- {{Greenwood&Earnshaw}}
- [https://ntp.niehs.nih.gov/go/tr462abs U.S. Department of Health and Human Services National Toxicology Program]
- [http://www.imoa.info/index.html International Molybdenum Association]
- [http://periodic.lanl.gov/42.shtml Los Alamos National Laboratory – "Molybdenum"]
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{{Molybdenum compounds}}
{{Oxides}}
{{oxygen compounds}}