Molybdenum dioxide is the chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 MoO₂. It is a violet-colored solid and is a metallic conductor. It crystallizes in a monoclinic cell, and has a distorted rutile, (TiO₂

Titanium dioxide

Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...

) crystal structure. In TiO₂ the oxide

Oxide

An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

 anions are close packed

Close-packing

In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement . Carl Friedrich Gauss proved that the highest average density – that is, the greatest fraction of space occupied by spheres – that can be achieved by a regular lattice...

 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
  Molybdenum(VI) oxide
  Molybdenum trioxide is chemical compound with the formula MoO3. This compound is produced on the largest scale of any molybdenum compound. It occurs as the rare mineral molybdite...
  
   with Mo over the course of 70 hours at 800 °C. The tungsten
  Tungsten
  Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
  
   analogue, WO₂, is prepared similarly.

2 MoO₃ + Mo → 3 MoO₂

• by reducing MoO₃ with H₂
  Hydrogen
  Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
  
   or NH₃
  Ammonia
  Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
  
   below 470°C

Single crystals are obtained by chemical transport

Chemical transport reaction

In chemistry, a chemical transport reaction describes a process for purification and crystallization of non-volatile solids. The process is also responsible for certain aspects of mineral growth from the effluent of volcanoes. The technique is distinct from chemical vapor deposition, which...

 using iodine

Iodine

Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

. Iodine reversibly converts MoO₂ into the volatile species MoO₂I₂.

Molybdenum oxide is a constituent of "technical molybdenum oxide" produced during the industrial processing of MoS₂:

2 MoS₂ + 7O₂ → 2MoO₃ + 4SO₂

MoS₂ + 6MoO₃ → 7MoO₂ + 2SO₂

2 MoO₂ + O₂ → 2MoO₃

MoO₂ has been reported as catalysing the dehydrogenation of alcohols and the reformation of hydrocarbons. Molybdenum nano-wires have been produced by reducing MoO₂ deposited on graphite

Mineralogical form of this compound is called tugarinovite, only very rarely found.