Difference between revisions 6001598 and 6001599 on simplewiki

{{chembox
| Watchedfields = changed
| verifiedrevid = 310175235
| ImageFileL1 = Ferrocene-2D.png
| ImageSizeL1 = 80 px
| ImageFileR1 = Ferrocene-from-xtal-3D-balls.png
| ImageSizeR1 = 120 px
| ImageFile2 = Photo of Ferrocene (powdered).JPG
| ImageSize2 = 220 px
| ImageName2 = Powdered Ferrocene
| IUPACName = ferrocene, bis(η<sup>5</sup>-cyclopentadienyl)iron
| OtherNames = dicyclopentadienyl iron 
| Section1 = {{Chembox Identifiers
|   CASNo_Ref = {{cascite}}
| CASNo = 102-54-5
|   PubChem = 11985121
|   ChEBI = 30672
|   SMILES = 
|   InChI = InChI=1/2C5H5.Fe/c2*1-2-4-5-3-1;/h2*1-5H;
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>10</sub>H<sub>10</sub>Fe
|   MolarMass = 186.04 g/mol
|   Appearance = light orange powder
|   Density = 1.107 g/cm<sup>3</sup> (0°C), 1.490 g/cm<sup>3</sup> (20 °C)<ref>{{cite web|url=http://www.chemicalbook.com/ProductMSDSDetailCB1414721_EN.htm|title=Ferrocene(102-54-5)|accessdate=3 February 2010}}</ref>
|   MeltingPt = 174 °C
|   BoilingPt = 249 °C
|   Solubility = Insoluble in water, soluble in most organic solvents
  }}
| Section3 = {{Chembox Hazards
|   MainHazards = 
|   FlashPt = 
|   Autoignition = 
  }}
| Section8 = {{Chembox Related
| OtherCpds = [[cobaltocene]], [[nickelocene]], [[chromacene]], [[bis(benzene)chromium]]}}
}}

'''Ferrocene''' is an [[organometallic compound]] with the formula Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>.   It is the prototypical [[metallocene]], a type of [[organometallic chemistry|organometallic]] [[chemistry|chemical]] compound consisting of two [[cyclopentadienyl complex|cyclopentadienyl]] rings bound on opposite sides of a central [[metal]] atom.   Such organometallic compounds are also known as [[sandwich compound]]s.<ref>{{cite journal|author=R. Dagani |url=http://pubs.acs.org/isubscribe/journals/cen/79/i49/html/7949sci1.html | title=Fifty Years of Ferrocene Chemistry| journal=[[Chemical and Engineering News]] |date=3 December 2001|volume= 79 |issue= 49 | pages = 37–38 |format=Subscription required}}</ref>  The rapid growth of [[organometallic chemistry]] is often attributed to the excitement arising from the discovery of ferrocene and its many [[Analog (chemistry)|analogues]].

==History==
[[File:Ferrocene kealy.svg|thumb|left|Pauson and Kealy's original (incorrect) notion of ferrocene's molecular structure]]
Ferrocene was first prepared unintentionally.   In 1951, Pauson and Kealy at [[Duquesne University]] reported the reaction of cyclopentadienyl magnesium bromide and [[iron(III) chloride|ferric chloride]] with the goal of oxidatively coupling the diene to prepare [[fulvalene]]. Instead, they obtained a light orange powder of "remarkable stability."<ref>{{cite journal
 | author = T. J. Kealy, P. L. Pauson
 | title = A New Type of Organo-Iron Compound
 | journal = Nature
 | year = 1951 
 | volume = 168 
 | pages = 1039
(contracted; show full)
 | title = Ferrocene: Ironclad History or Rashomon Tale?
 | journal = Angewandte Chemie International Edition
 | year = 2000
 | volume = 39
 | pages = 123–124
 | doi = 10.1002/(SICI)1521-3773(20000103)39:1<123::AID-ANIE123>3.0.CO;2-Z}}</ref> Its distinctive "sandwich" structure led to an explosion of interest in compounds of [[d-block]] metals with hydrocarbons, and invigorated the development of the flourishing study of organometallic chemistry.
   In 1973 [[Ernst Otto Fischer|Fischer]] of the [[Technische Universität München]] and [[Geoffrey Wilkinson|Wilkinson]] of [[Imperial College London]] shared a Nobel Prize for their work on metallocenes and other aspects of organometalic chemistry.<ref>{{cite web |url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1973/press.html |title= Press Release: The Nobel Prize in Chemistry 1973 |year= 1973 |publisher= The Royal Swedish Academy of Sciences}}</ref>

==Structure and bonding==
The iron atom in ferrocene is normally assigned to the +2 oxidation state, as can be shown using [[Mössbauer spectroscopy]]. Each cyclopentadienyl (Cp) ring is then allocated a single negative charge, bringing the number of π-electrons on each ring to six, and thus making them [[aromaticity|aromatic]].   These twelve electrons (six from each ring) are then shared with the metal ''via'' covalent bonding, which, when combined with the six ''d''-electrons on Fe<sup>2+</sup>, results in the complex having an [[18-electron rule|18-electron]], [[noble gas]] electron configuration.

(contracted; show full)
 | journal = [[e-Journal of Surface Science and Nanotechnology]]
 | year = 2008
 | volume = 6
 | pages = 119–123
 | doi = 10.1380/ejssnt.2008.119}}</ref><ref>[http://www.jstage.jst.go.jp/article/ejssnt/6/0/119/_pdf Self-Assembling Properties of 11-Ferrocenyl-1-Undecanethiol on Highly Oriented Pyrolitic Graphite Characterized by Scanning Tunneling Microscopy]
}}</ref>

The carbon-carbon bond distances are 1.40 Å within the five membered rings, and the Fe-C bond distances are 2.04 Å.

==Synthesis and handling properties==
Ferrocene is efficiently prepared by the reaction of [[sodium cyclopentadienide]] with anhydrous [[iron(II) chloride|ferrous chloride]] in ethereal solvents:<ref>{{OrgSynth | title = Ferrocene | author = [[Geoffrey Wilkinson]] | collvol = 4 | collvolpages = 473 | year = 1963 | prep = cv4p0473}}</ref>
:2 NaC<sub>5</sub>H<sub>5</sub>  +  FeCl<sub>2</sub>   →   Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>  +  2 NaCl
[[Image:Ferrocene 3d model 2.png|thumb|right|A space-filling model of ferrocene.]]
As expected for a symmetric and uncharged species, ferrocene is soluble in normal organic solvents, such as benzene, but is insoluble in water.   Ferrocene is an [[air]]-stable orange solid that readily [[Sublimation (physics)|sublime]]s, especially upon heating in a vacuum.   It is stable to temperatures as high as 400 °C.<ref>Solomons, Graham, and Craig Fryhle. Organic Chemistry. 9th ed. USA: John Wiley & Sons, Inc., 2006.</ref>  The following table gives typical values of vapor pressure of ferrocene at different temperatures:<ref>Monte, M. J. S.; Santos, L. M. N. B. F.; Fulem, M.; Fonseca, J. M. S. & Sousa, C. A. D.,   New static apparatus and vapor pressure of reference materials: Naphthalene, benzoic acid, benzophenone, and ferrocene,  [[J. Chem. Eng. Data]], 2006, 51, 757-766</ref>
{| class="wikitable"
|-
! pressure(Pa)
! 1
! 10
! 100
|-
| temperature(K)
| 298
| 323
| 353
|}

==Reactions==
===With electrophiles===
Ferrocene undergoes many reactions characteristic of aromatic compounds, enabling the preparation of substituted derivatives.   A common undergraduate experiment is the [[Friedel-Crafts reaction]] of ferrocene with [[acetic anhydride]] (or [[acetyl chloride]]) in the presence of [[phosphoric acid]] as a catalyst.
[[Image:FcGen'l.png|400px|thumb|center|Important reactions of ferrocene with electrophiles and other reagents.]]

===Lithiation===
Ferrocene reacts readily with [[butyl lithium]] to give 1,1'-dilithioferrocene, which in turn is a versatile [[nucleophile]]. This approach is especially useful method to introduce main group functionality, e.g. using S8, chlorophosphines, chlorosilanes.   The strained compounds undergo [[ring-opening polymerization]].<ref>David E. Herbert, Ulrich F. J. Mayer, Ian Manners “Strained Metallocenophanes and Related Organometallic Rings Containing pi-Hydrocarbon Ligands and Transition-Metal Centers”  Angew. Chem. Int. Ed. 2007, volume 46, 5060 - 5081.   {{DOI|10.1002/anie.200604409}}</ref>

[[Image:FcLi2chem.png|450px|thumb|center|Some transformations of dilithioferrocene.]]

===Phosphorus derivatives===
Many phosphine derivatives of ferrocenes are known and some are used in commericialized processes.   Simplest and best known is [[1,1'-Bis(diphenylphosphino)ferrocene|1,1'-bis(diphenylphosphino)ferrocene]] (dppf) prepared from dilithioferrocene.   Other routes to such ligands are known.   For example, in the presence of [[aluminium chloride]]  Me<sub>2</sub>NPCl<sub>2</sub> and ferrocene react to give ferrocenyl dichloro[[phosphine]],<ref>{{cite journal
 | title = Ferrocene derivatives. 27. Ferrocenyldimethylphosphine
 | author = G.R. Knox, P.L. Pauson and D. Willison
 | journal = Organometallics
 | volume = 11
 | issue = 8
 | pages = 2930 &ndash; 2933
 | year = 1992
(contracted; show full)

==Stereochemistry==
A variety of substitution patterns are possible with ferrocene including substition at one or both of the rings. The most common substitution patterns are 1-substituted (one substituent on one ring) and 1,1'-disubstituted (one substituent on each ring).
   Usually the rings rotate freely, which simplifies the isomerism.   Disubstituted ferrocenes can exist as either 1,2- and 1,1' isomers, which are not interconvertaible.   1,2-Heterodisubstituted ferrocenes are chiral.

==Applications of ferrocene and its derivatives==
Ferrocene and its numerous derivatives have no large-scale applications, but have many niche uses that exploit the unusual structure (ligand scaffolds, pharmaceutical candidates), robustness (anti-knock formulations, precursors to materials), and redox (reagents and redox standards).

===Fuel additives===
Ferrocene and its derivatives are [[antiknock agent]]s used in the fuel for petrol engines; they are safer than [[tetraethyl lead]], previously used.<ref>[http://www.osd.org.tr/14.pdf Application of fuel additives]</ref> It is possible to buy at [[Halfords]] in   the UK,   a petrol additive solution which contains ferrocene which can be added to unleaded petrol to enable it to be used in vintage cars which were designed to run on leaded petrol.<ref>{{US patent|4104036}}</ref> The iron containing deposits formed from ferrocene can form a conductive coating on the spark plug surfaces.

In [[Diesel fuel|diesel]]-fuelled engines, ferrocene reduces the production of soot.

===Pharmaceutical===
(contracted; show full)

Ferrocene is also used as a nano-sized "loom" in the manufacture of ultra-high molecular weight polyethylene's very long fibers, which are used to manufacture newer types of bulletproof vest fabric.{{Citation needed|date=March 2008}}

===As a ligand scaffold===
Chiral ferrocenyl [[phosphine]]s are employed as ligands for transition-metal catalyzed reactions. Some of them have found industrial applications in the synthesis of pharmaceuticals and agrochemicals.
   For example, the [[diphosphine ligand|diphosphine]] [[1,1'-bis(diphenylphosphino)ferrocene]] (dppf) is a valuable ligand for [[palladium]]-[[coupling reaction]]s.

==Derivatives and variations==
Many other hydrocarbons can be used instead of cyclopentadienyl. For example, [[indene|indenyl]] can be used in place of the cyclopentadienyl to form bisbenzoferrocene.<ref>B.R. Waldbaum and R.C. Kerber, ''Inorg. Chim. Acta'', 1999, '''291''', 109 - 126.</ref>

[[Image:FcVarietyPack.png|400px|center|Various ferrocene derivatives where cyclopentadienyl has been replaced by related ligands]]

The carbon atoms can be replaced by heteroatoms as illustrated by [[Fe(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(η<sup>5</sup>-P<sub>5</sub>]] and [[Fe(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(η<sup>5</sup>-C<sub>4</sub>H<sub>4</sub>N)]] ("azaferrocene"). The latter arises from decarbonylation of [[Fe(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(CO)<sub>2</sub>(η<sup>1</sup>-pyrrole)]] in [[cyclohexane]].(a.<ref>J. Zakrzewski and C. Gianotti, ''J. Organomet. Chem.'', 1990, '''388''',175 - 180.</ref>. This compound on boiling under [[reflux]] in [[benzene]] is converted to ferrocene.<ref>A. Efraty, N. Jubran and A. Goldman, ''Inorg. Chem.'', 1982, '''21''', 868 - 873.</ref>

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