Editing Iron (section)

===Organometallic compounds===
[[File:Sample of iron pentacarbonyl.jpg|thumb|upright=0.36|left|Iron penta-<br/>carbonyl]]
[[Organoiron chemistry]] is the study of [[organometallic compound]]s of iron, where carbon atoms are covalently bound to the metal atom. They are many and varied, including [[cyanometallate|cyanide complexes]], [[carbonyl complex]]es, [[sandwich compound|sandwich]] and [[half-sandwich compound]]s.

[[File:Prussian blue.jpg|thumb|right|Prussian blue]]
[[Prussian blue]] or "ferric ferrocyanide", Fe<sub>4</sub>[Fe(CN)<sub>6</sub>]<sub>3</sub>, is an old and well-known iron-cyanide complex, extensively used as pigment and in several other applications. Its formation can be used as a simple wet chemistry test to distinguish between aqueous solutions of Fe<sup>2+</sup> and Fe<sup>3+</sup> as they react (respectively) with [[potassium ferricyanide]] and [[potassium ferrocyanide]] to form Prussian blue.<ref name="HollemanAF" />

Another old example of an organoiron compound is [[iron pentacarbonyl]], Fe(CO)<sub>5</sub>, in which a neutral iron atom is bound to the carbon atoms of five [[carbon monoxide]] molecules. The compound can be used to make [[carbonyl iron]] powder, a highly reactive form of metallic iron. [[Thermal decomposition|Thermolysis]] of iron pentacarbonyl gives [[triiron dodecacarbonyl]], {{chem2|Fe3(CO)12}}, a complex with a cluster of three iron atoms at its core. Collman's reagent, [[disodium tetracarbonylferrate]], is a useful reagent for organic chemistry; it contains iron in the −2 oxidation state. [[Cyclopentadienyliron dicarbonyl dimer]] contains iron in the rare +1 oxidation state.<ref>{{Greenwood&Earnshaw1st|pages=1282–86}}.</ref>

{{multiple image
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| image1 = Ferrocene.svg
| image2 = Photo of Ferrocene (powdered).JPG
| footer = Structural formula of ferrocene and a powdered sample
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A landmark in this field was the discovery in 1951 of the remarkably stable [[sandwich compound]] [[ferrocene]] {{chem2|Fe(C5H5)2}}, by Pauson and Kealy<ref>{{Cite journal |last1= Kealy |first1=T.J. |last2= Pauson |first2=P.L. |year= 1951 |title= A New Type of Organo-Iron Compound |journal= [[Nature (journal)|Nature]] |volume= 168 |issue= 4285 |pages= 1039–40 |doi= 10.1038/1681039b0|bibcode = 1951Natur.168.1039K |s2cid=4181383 }}</ref> and independently by Miller and colleagues,<ref name = Miller>{{cite journal| last1=Miller|first1= S. A.|last2=Tebboth|first2= J. A.|last3= Tremaine|first3= J. F.|journal= [[Journal of the Chemical Society|J. Chem. Soc.]]|year=1952| pages= 632–635| title=114. Dicyclopentadienyliron |doi=10.1039/JR9520000632}}</ref> whose surprising molecular structure was determined only a year later by [[Robert Burns Woodward|Woodward]] and [[Geoffrey Wilkinson|Wilkinson]]<ref>{{cite journal |first1= G. |last1=Wilkinson|author1-link=Geoffrey Wilkinson |first2=M.|last2= Rosenblum |first3=M. C.|last3= Whiting|first4= R. B. |last4=Woodward|author4-link=Robert Burns Woodward |title = The Structure of Iron Bis-Cyclopentadienyl |journal = [[Journal of the American Chemical Society|J. Am. Chem. Soc.]] |year = 1952|volume = 74 |pages = 2125–2126 |doi = 10.1021/ja01128a527 |issue = 8|bibcode=1952JAChS..74.2125W }}</ref> and [[Ernst Otto Fischer|Fischer]].<ref>{{Cite journal|last=Okuda|first=Jun|date=2016-12-28|title=Ferrocene – 65 Years After|journal=European Journal of Inorganic Chemistry|volume=2017|issue=2|pages=217–219|doi=10.1002/ejic.201601323|issn=1434-1948|doi-access=free}}</ref>
Ferrocene is still one of the most important tools and models in this class.{{sfn|Greenwood|Earnshaw|1997|p=1104}}

Iron-centered organometallic species are used as [[catalyst]]s. The [[Knölker complex]], for example, is a [[transfer hydrogenation]] catalyst for [[ketone]]s.<ref>{{cite journal|last=Bullock|first=R.M.|date=11 September 2007|title=An Iron Catalyst for Ketone Hydrogenations under Mild Conditions|journal=[[Angew. Chem. Int. Ed.]]|volume=46|issue=39|pages=7360–63|doi=10.1002/anie.200703053|pmid=17847139|doi-access=free}}</ref>