Editing Molybdenum (section)

==Compounds==
{{Category see also|Molybdenum compounds}}
Molybdenum forms chemical compounds in oxidation states −4 and from −2 to +6. Higher oxidation states are more relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with [[metal cluster]]s, and very low oxidation states are typically associated with [[organomolybdenum compound]]s. The chemistry of molybdenum and tungsten show strong similarities. The relative rarity of molybdenum(III), for example, contrasts with the pervasiveness of the chromium(III) compounds. The highest oxidation state is seen in [[molybdenum(VI) oxide]] (MoO<sub>3</sub>), whereas the normal sulfur compound is [[molybdenum disulfide]] MoS<sub>2</sub>.<ref name="Holl" />

{|class="wikitable" style="float:left; margin-right: 1em;"
|-
!Oxidation <br />state
!Example<ref name="Schmidt">{{Cite book |last=Hofmann |first=Karl A. |chapter-url=https://doi.org/10.1007/978-3-663-14240-9_31 |title=Anorganische Chemie |date=1973 |publisher=Vieweg+Teubner Verlag |isbn=978-3-663-14240-9 |editor-last=Hofmann |editor-first=Karl A. |location=Wiesbaden |pages=627–641 |language=de |chapter=VI. Nebengruppe |doi=10.1007/978-3-663-14240-9_31 |editor-last2=Hofmann |editor-first2=Ulrich |editor-last3=Rüdorff |editor-first3=Walter}}</ref><ref name="auto">{{Cite book |last=Werner |first=Helmut |url=https://books.google.com/books?id=dP4LTfaPzAMC |title=Landmarks in Organo-Transition Metal Chemistry: A Personal View |date=2008 |publisher=Springer Science & Business Media |isbn=978-0-387-09848-7 |language=en}}</ref>
|-
| −4||{{chem|Na|4|[Mo|(CO)|4|]}}
|-
| −2||{{chem|[Mo|(CO)|5|]|2-}}<ref>{{Cite journal
 | title = Metal Carbonyl Anions: from [Fe(CO)<sub>4</sub>]<sup>2−</sup> to [Hf(CO)<sub>6</sub>]<sup>2−</sup> and Beyond
 | author = Ellis, J. E.
 | journal = [[Organometallics]]
 | year = 2003 | volume = 22 | issue = 17 | pages = 3322–3338
 | doi = 10.1021/om030105l
}}</ref>
|-
| −1||{{chem|Na|2|[Mo|2|(CO)|10|]}}
|-
| 0||[[Molybdenum hexacarbonyl|{{chem|Mo(CO)|6|}}]]
|-
| +1||[[Cyclopentadienylmolybdenum tricarbonyl|{{chem|C|5|H|5|Mo(CO)|3}}]]
|-
| +2||[[Molybdenum(II) chloride|{{chem|MoCl|2}}]]
|-
| +3||[[Molybdenum(III) bromide|{{chem|MoBr|3}}]]
|-
| '''+4'''||[[Molybdenum disulfide|{{chem|MoS|2}}]]
|-
| +5||[[Molybdenum(V) chloride|{{chem|MoCl|5}}]]
|-
| '''+6'''||[[Molybdenum(VI) fluoride|{{chem|MoF|6}}]]
|}
[[File:Phosphotungstate-3D-polyhedra.png|thumb|upright|[[Keggin structure]] of the phosphomolybdate anion (P[Mo<sub>12</sub>O<sub>40</sub>]<sup>3−</sup>), an example of a [[polyoxometalate]]]]

From the perspective of commerce, the most important compounds are molybdenum disulfide ({{chem|MoS|2}}) and molybdenum trioxide ({{chem|MoO|3}}). The black disulfide is the main mineral. It is roasted in air to give the trioxide:<ref name="Holl" />

:2 {{chem|MoS|2}} + 7 {{chem|O|2}} → 2 {{chem|MoO|3}} + 4 {{chem|SO|2}}

The trioxide, which is volatile at high temperatures, is the precursor to virtually all other Mo compounds as well as alloys. Molybdenum has several [[oxidation state]]s, the most stable being +4 and +6 (bolded in the table at left).

Molybdenum(VI) oxide is soluble in strong [[base (chemistry)|alkaline]] water, forming molybdates (MoO<sub>4</sub><sup>2−</sup>). Molybdates are weaker oxidants than [[chromates]]. They tend to form structurally complex [[oxyanion]]s by condensation at lower [[pH]] values, such as [Mo<sub>7</sub>O<sub>24</sub>]<sup>6−</sup> and [Mo<sub>8</sub>O<sub>26</sub>]<sup>4−</sup>. Polymolybdates can incorporate other ions, forming [[polyoxometalate]]s.<ref>{{cite journal|journal = Angewandte Chemie International Edition|volume = 30|pages=34–48|date = 1997|title = Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines|first1 = Michael T.|last1 = Pope|last2= Müller |first2 = Achim|doi = 10.1002/anie.199100341}}</ref> The dark-blue [[phosphorus]]-containing heteropolymolybdate P[Mo<sub>12</sub>O<sub>40</sub>]<sup>3−</sup> is used for the [[ultraviolet-visible spectroscopy|spectroscopic]] detection of phosphorus.<ref>{{cite book|isbn = 978-0-8247-8433-1|pages = 280–288|editor = Nollet, Leo M. L.|date = 2000|publisher = Marcel Dekker|location = New York, NY|title = Handbook of water analysis|url=https://books.google.com/books?id=YZpW4Y4Q_PIC&pg=PA280}}</ref> 

The broad range of [[oxidation state]]s of molybdenum is reflected in various molybdenum chlorides:<ref name="Holl" />
* [[Molybdenum(II) chloride]] MoCl<sub>2</sub>, which exists as the hexamer Mo<sub>6</sub>Cl<sub>12</sub> and the related dianion [Mo<sub>6</sub>Cl<sub>14</sub>]<sup>2-</sup>.
* [[Molybdenum(III) chloride]] MoCl<sub>3</sub>, a dark red solid, which converts to the anion trianionic complex [MoCl<sub>6</sub>]<sup>3-</sup>.
* [[Molybdenum tetrachloride|Molybdenum(IV) chloride]] MoCl<sub>4</sub>, a black solid, which adopts a polymeric structure.
* [[Molybdenum(V) chloride]] MoCl<sub>5</sub> dark green solid, which adopts a dimeric structure.
* [[Molybdenum(VI) chloride]] MoCl<sub>6</sub> is a black solid, which is monomeric and slowly decomposes to MoCl<sub>5</sub> and Cl<sub>2</sub> at room temperature.<ref>{{Cite journal|last1=Tamadon|first1=Farhad|last2=Seppelt|first2=Konrad|date=2013-01-07|title=The Elusive Halides VCl 5, MoCl 6, and ReCl 6|journal=Angewandte Chemie International Edition|language=en|volume=52|issue=2|pages=767–769|doi=10.1002/anie.201207552|pmid=23172658}}</ref>

The accessibility of these oxidation states depends quite strongly on the halide counterion: although [[molybdenum(VI) fluoride]] is stable, molybdenum does not form a stable hexachloride, pentabromide, or tetraiodide.<ref>{{Kirk-Othmer|doi=10.1002/0471238961.1315122519200905.a01.pub3|title=Molybdenum Compounds|first=Edward&nbsp;I.|last=Stiefel}}</ref>  

Like [[chromium]] and some other transition metals, molybdenum forms [[quadruple bond]]s, such as in Mo<sub>2</sub>(CH<sub>3</sub>COO)<sub>4</sub> and [Mo<sub>2</sub>Cl<sub>8</sub>]<sup>4−</sup>.<ref name="Holl" /><ref>{{Cite book|title=Inorganic Syntheses: Volume 36 |last1=Walton |first1=Richard A. |last2=Fanwick |first2=Phillip E. |last3=Girolami |first3=Gregory S. |last4=Murillo |first4=Carlos A. |last5=Johnstone |first5=Erik V. |date=2014 |publisher=John Wiley & Sons |isbn=978-1118744994 |editor-last=Girolami |editor-first=Gregory S. |pages=78–81 |language=en |doi=10.1002/9781118744994.ch16 |editor-last2=Sattelberger |editor-first2=Alfred P.}}</ref> The [[ECW model|Lewis acid]] properties of the butyrate and perfluorobutyrate dimers, [[ECW model|Mo<sub>2</sub>(O<sub>2</sub>CR)<sub>4</sub>]] and Rh<sub>2</sub>(O<sub>2</sub>CR) <sub>4</sub>, have been reported.<ref>{{Cite journal |last1=Drago |first1=Russell S. |last2=Long |first2=John R. |last3=Cosmano |first3=Richard |date=1982-06-01 |title=Comparison of the coordination chemistry and inductive transfer through the metal-metal bond in adducts of dirhodium and dimolybdenum carboxylates |journal=Inorganic Chemistry |language=en |volume=21 |issue=6 |pages=2196–2202 |doi=10.1021/ic00136a013 |issn=0020-1669}}</ref>

The oxidation state 0 and lower are possible with carbon monoxide as ligand, such as in [[molybdenum hexacarbonyl]], Mo(CO)<sub>6</sub>.<ref name="Holl" /><ref name="auto"/>