|Molar mass||127.94 g/mol|
|Melting point||1,100 °C (2,010 °F; 1,370 K) decomposes|
|Solubility||insoluble in alkalies, HCl, HF
slightly soluble in hot H2SO4
|Distorted rutile (tetragonal)|
|Octahedral (MoIV); trigonal (O−II)|
|EU Index||Not listed|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is: / ?)(|
Molybdenum dioxide is the chemical compound with the formula MoO2. It is a violet-colored solid and is a metallic conductor. It crystallizes in a monoclinic cell, and has a distorted rutile, (TiO2) crystal structure. In TiO2 the oxide anions are close packed and titanium atoms occupy half of the octahedral interstices (holes). In MoO2 the octahedra are distorted, the Mo atoms are off-centre, leading to alternating short and long Mo – Mo distances and Mo-Mo bonding. The short Mo – Mo distance is 251 pm which is less than the Mo – Mo distance in the metal, 272.5 pm. The bond length is shorter than would be expected for a single bond. The bonding is complex and involves a delocalisation of some of the Mo electrons in a conductance band accounting for the metallic conductivity.
MoO2 can be prepared :
- by reduction of MoO3 with Mo over the course of 70 hours at 800 °C. The tungsten analogue, WO2, is prepared similarly.
- 2 MoO3 + Mo → 3 MoO2
- 2 MoS2 + 7O2 → 2MoO3 + 4SO2
- MoS2 + 6MoO3 → 7MoO2 + 2SO2
- 2 MoO2 + O2 → 2MoO3
MoO2 has been reported as catalysing the dehydrogenation of alcohols, the reformation of hydrocarbons and biodiesel. Molybdenum nano-wires have been produced by reducing MoO2 deposited on graphite
Mineralogical form of this compound is called tugarinovite, only very rarely found.
- Oxides: Solid state chemistry McCarroll W.H. Encyclopedia of Inorganic Chemistry Ed R. Bruce King, (1994), John Wiley & sons ISBN 0-471-93620-0
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- Conroy, L. E.; Ben-Dor, L. "Molybdenum(IV) Oxide and Tungsten(IV) Oxides Single-Crystals" Inorganic Syntheses 1995, volume 30, pp. 105–107. ISBN 0-471-30508-1
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- Catalytic partial oxidation of a biodiesel surrogate over molybdenum dioxide, C.M. Cuba-Torres, et al, Fuel (2015), doi:10.1016/j.fuel.2015.01.003
- Synthesis of Molybdenum Nanowires with Millimeter-Scale Lengths Using Electrochemical Step Edge Decoration M. P. Zach, K. Inazu, K. H. Ng, J. C. Hemminger, and R. M. Penner Chem. Mater. (2002),14, 3206 doi:10.1021/cm020249a