Editing Organometallic chemistry (section)

== Organometallic compounds ==

[[File:Magnesium bis-cyclopentadienyl bottle.jpg|180px|thumb|right|A steel bottle containing MgCp<sub>2</sub> [[magnesocene|(magnesium bis-cyclopentadienyl)]], which, like several other organometallic compounds, is pyrophoric in air.]]

Organometallic compounds are distinguished by the prefix "organo-" (e.g., organopalladium compounds), and include all compounds which contain a bond between a metal atom and a carbon atom of an [[organyl group]].<ref name=":0" /> In addition to the traditional metals ([[alkali metal]]s, [[alkali earth metal]]s, [[transition metals]], and [[post transition metals]]), [[lanthanide]]s, [[actinide]]s, semimetals, and the elements [[boron]], [[silicon]], [[arsenic]], and [[selenium]] are considered to form organometallic compounds.<ref name=":0" /> Examples of organometallic compounds include [[Gilman reagent]]s, which contain [[lithium]] and [[copper]], and [[Grignard reagent]]s, which contain [[magnesium]]. Boron-containing organometallic compounds are often the result of [[hydroboration]] and [[carboboration]] reactions. [[Tetracarbonyl nickel]] and [[ferrocene]] are examples of organometallic compounds containing [[transition metal]]s. Other examples of organometallic compounds include [[organolithium]] compounds such as [[n-butyllithium|''n''-butyllithium]] (n-BuLi), [[organozinc]] compounds such as [[diethylzinc]] (Et<sub>2</sub>Zn), [[organotin]] compounds such as [[tributyltin hydride]] (Bu<sub>3</sub>SnH), [[organoborane]] compounds such as [[triethylborane]] (Et<sub>3</sub>B), and [[organoaluminium]] compounds such as [[trimethylaluminium]] (Me<sub>3</sub>Al).<ref name=ChrisE/>

A naturally occurring organometallic complex is [[methylcobalamin]] (a form of [[Vitamin B12|Vitamin B<sub>12</sub>]]), which contains a [[cobalt]]-[[methyl]] bond. This complex, along with other biologically relevant complexes are often discussed within the subfield of [[bioorganometallic chemistry]].{{sfn|Lippard|Berg|1994|p={{pn|date=October 2021}}}}

<gallery widths="140" heights="96" caption="Representative Organometallic Compounds">
File:Ferrocene.svg|[[Ferrocene]] is an archetypal organoiron complex.  It is an air-stable, sublimable compound.
File:Cobaltocene.svg|[[Cobaltocene]] is a structural analogue of ferrocene, but is highly reactive toward air.
File:HRh(CO)P3again.png|[[Tris(triphenylphosphine)rhodium carbonyl hydride]] is used in the commercial production of many aldehyde-based [[fragrance]]s.
File:Zeise'sSalt.png|[[Zeise's salt]] is an example of a [[transition metal alkene complex]].
File:Trimethylaluminium-from-xtal-3D-bs-17.png|[[Trimethylaluminium]] is an organometallic compound with a [[Bridging ligand|bridging]] [[methyl group]].  It is used in the industrial production of some alcohols.
File:Dimethylzinc-3D-balls.png|[[Dimethylzinc]] has a linear coordination. It is a volatile pyrophoric liquid that is used in the preparation of semiconducting films.
File:Lithium-diphenylcuprate-etherate-dimer-from-xtal-2D-skeletal.png|Lithium diphenylcuprate bis(diethyl etherate) is an example of a [[Gilman reagent]], a type of organocopper complex frequently employed in organic synthesis.
File:AdoCbl-ColorCoded.png|[[Adenosylcobalamin]] is a [[Cofactor (biochemistry)|cofactor]] required by several crucial enzymatic reactions that take place in the human body.  It is a rare example of a metal (cobalt) alkyl in biology.
File:IronPentacarbonylStructure.png|[[Iron pentacarbonyl|Iron(0) pentacarbonyl]] is a red-orange liquid prepared directly from the union of finely divided iron and carbon monoxide gas under pressure.
File:Tc99 sestamibi 2D structure.svg|[[Technetium (99mTc) sestamibi|Technetium[<sup>99m</sup>Tc] sestamibi]] is used to image the heart muscle in nuclear medicine.
</gallery>

===Distinction from coordination compounds with organic ligands===
Many [[Complex (chemistry)|complex]]es feature [[coordination bond]]s between a metal and organic [[ligands]]. Complexes where the organic ligands bind the metal through a [[heteroatom]] such as oxygen or nitrogen are considered coordination compounds (e.g., [[heme A]] and [[Tris(acetylacetonato)iron(III)|Fe(acac)<sub>3</sub>]]). However, if any of the ligands form a direct metal-carbon (M-C) bond, then the complex is considered to be organometallic. Although the IUPAC has not formally defined the term, some chemists use the term "metalorganic" to describe any coordination compound containing an organic ligand regardless of the presence of a direct M-C bond.<ref>{{cite book |doi=10.1016/B978-0-12-409547-2.13135-X |chapter=Metalorganic Functionalization in Vacuum |title=Encyclopedia of Interfacial Chemistry |year=2018 |last1=Rodríguez-Reyes |first1=J.C.F. |last2=Silva-Quiñones |first2=D. |pages=761–768 |isbn=978-0-12-809894-3 }}</ref>

The status of compounds in which the [[resonance (chemistry)|canonical anion]] has a negative charge that is shared between ([[delocalized electrons|delocalized]]) a carbon atom and an atom more [[electronegativity|electronegative]] than carbon (e.g. [[enolate]]s) may vary with the nature of the anionic moiety, the metal ion, and possibly the medium. In the absence of direct structural evidence for a carbon–metal bond, such compounds are not considered to be organometallic.<ref name=":0" />  For instance, lithium enolates often contain only Li-O bonds and are not organometallic, while zinc enolates ([[Reformatsky reaction|Reformatsky reagents]]) contain both Zn-O and Zn-C bonds, and are organometallic in nature.<ref name=ChrisE/>

===Structure and properties===
The metal-carbon bond in organometallic compounds is generally highly [[covalent]].{{sfn|Crabtree|2009|p={{pn|date=October 2021}}}} For highly electropositive elements, such as lithium and sodium, the carbon ligand exhibits [[carbanion]]ic character, but free carbon-based anions are extremely rare, an example being [[cyanide]].
[[File:Mn(II) kompleksi monokoristall.jpg|thumb|a single crystal of a Mn(II) complex, [BnMIm]4[MnBr4]Br2. Its bright green color originates from spin-forbidden d-d transitions]]
Most organometallic compounds are solids at room temperature, however some are liquids such as [[methylcyclopentadienyl manganese tricarbonyl]], or even [[volatility (chemistry)|volatile]] liquids such as [[nickel tetracarbonyl]].{{sfn|Crabtree|2009|p={{pn|date=October 2021}}}} Many organometallic compounds are [[Air sensitivity|air sensitive]] (reactive towards oxygen and moisture), and thus they must be handled under an [[Inert gas|inert atmosphere]].{{sfn|Crabtree|2009|p={{pn|date=October 2021}}}} Some organometallic compounds such as [[triethylaluminium]] are [[Pyrophoricity|pyrophoric]] and will [[Combustion|ignite]] on contact with air.<ref>{{Cite web|last=|first=|date=2016-05-24|title=Triethylaluminium – SDS|url=https://www.chemblink.com/MSDS/MSDSFiles/97-93-8_Sigma-Aldrich.pdf|archive-url=https://web.archive.org/web/20220125201058/https://www.chemblink.com/MSDS/MSDSFiles/97-93-8_Sigma-Aldrich.pdf|archive-date=25 January 2022|access-date=2021-01-03|website=chemBlink|url-status=dead}}</ref>