Molybdenum dioxide is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

MoO. It is a violet-colored solid and is a metallic conductor. The mineralogical form of this compound is called tugarinovite, and is only very rarely found.

Structure

It crystallizes in a

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

cell, and has a distorted rutile, ( TiO₂) crystal structure. In TiO the

oxide 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 (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

anions are close packed and titanium atoms occupy half of the octahedral interstices (holes). In MoO 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.

Preparation

MoO can be prepared : *by reduction of MoO₃ with Mo over the course of 70 hours at . The

tungsten Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...

analogue, WO, is prepared similarly. :2 MoO + Mo → 3 MoO *by reducing MoO with H₂ or NH₃ below Single crystals are obtained by chemical transport using

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

. Iodine reversibly converts MoO₂ into the volatile species MoOI.

Uses

Molybdenum dioxide is a constituent of "technical molybdenum trioxide" produced during the industrial processing of MoS₂: :2 MoS + 7 O → 2 MoO + 4 SO :MoS + 6 MoO → 7 MoO + 2 SO :2 MoO + O → 2 MoO MoO has been reported as catalysing the dehydrogenation of alcohols, the reformation of hydrocarbons and biodiesel. Molybdenum nano-wires have been produced by reducing MoO deposited on graphite. Molybdenum dioxide has also been suggested as possible anode material for Li-ion batteries.

References

{{oxygen compounds molybdenum(IV) compounds transition metal oxides