Difference between revisions 6001600 and 6001601 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
 | |doi = 10.1038/1681039b0}}</ref> This stability was accorded to the aromatic character of the negative charged cyclopentadienyls, but the sandwich structure of the η<sup>5</sup> (pentahapto) compound was not recognized by them.

[[Robert Burns Woodward]] and [[Geoffrey Wilkinson]] deduced the structure based on its reactivity.<ref>{{cite journal
 | |author = G. Wilkinson, M. Rosenblum, M. C. Whiting, R. B. Woodward
 | |title = The Structure of Iron Bis-Cyclopentadienyl
 | |journal = [[Journal of the American Chemical Society]]
 | |year = 1952
 | |volume = 74
 | |pages = 2125–2126
 | |doi = 10.1021/ja01128a527}}</ref> Independently [[Ernst Otto Fischer]] also came to the conclusion of the sandwich structure and started to synthesize other metallocenes such as [[nickelocene]] and [[cobaltocene]].<ref>{{cite journal
 | |author = E. O. Fischer, W. Pfab
 | |title = Zur Kristallstruktur der Di-Cyclopentadienyl-Verbindungen des zweiwertigen Eisens, Kobalts und Nickels 
 | |journal = Z. Naturforsch. B
 | |year = 1952
 | |volume = 7
 | |pages = 377–379
 | |doi =  }}</ref>   Ferrocene's structure was confirmed by [[Nuclear magnetic resonance|NMR]] spectroscopy and [[X-ray crystallography]].<ref>{{cite journal
 | |author = J. Dunitz, L. Orgel, A. Rich
 | |title = The crystal structure of ferrocene
 | |journal = [[Acta Crystallographica]]
 | |year = 1956
 | |volume = 9
 | |pages = 373–5
 | |doi = 10.1107/S0365110X56001091}}</ref><ref>{{cite journal
 | |author = Pierre Laszlo, Roald Hoffmann,
 | |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 (contracted; show full)

The lack of individual bonds between the carbon atoms of the Cp ring and the Fe<sup>2+</sup> ion results in the Cp rings to freely rotate about the Cp<sub>(centroid)</sub>-Fe-Cp<sub>(centroid)</sub> axis, as observed by [[
Nnuclear Mmagnetic Rresonance]]<ref>{{cite journal
 | |author = E. W. Abel, N. J. Long, K. G. Orrell, A. G. Osborne, V. Sik
 | |title = Dynamic NMR studies of ring rotation in substituted ferrocenes and ruthenocenes
 | |journal = [[Journal of Organometallic Chemistry]]
 | |year = 1991
 | |volume = 403
 | |pages = 195–208
 | |doi = 10.1016/0022-328X(91)83100-I}}</ref> and [[Sscanning Ttunneling Mmicroscopy]].<ref>{{cite journal
 | |author = L. F. N. Ah Qune, K. Tamada, M. Hara
 | |title = Self-Assembling Properties of 11-Ferrocenyl-1-Undecanethiol on Highly Oriented Pyrolitic Graphite Characterized by Scanning Tunneling Microscopy
 | |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{{cite journal|doi=10.1021/je050502y}}</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 commercialized 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
 | |doi = 10.1021/om00044a038
}}</ref>
while treatment with [[phenyldichlorophosphine]] under similar conditions forms ''P,P''-diferrocenyl-''P''-phenyl phosphine.<ref>{{cite journal
 | |author = G.P. Sollott, H.E. Mertwoy, S. Portnoy and J.L. Snead
 | |title = Unsymmetrical Tertiary Phosphines of Ferrocene by Friedel-Crafts Reactions. I. Ferrocenylphenylphosphines 
 | |journal = J. Org. Chem.
 | |year = 1963 
 | |volume = 28 
 | |pages = 1090 &ndash; –1092
 | |doi = 10.1021/jo01039a055
}}</ref> In common with [[anisole]] the reaction of ferrocene with P<sub>4</sub>S<sub>10</sub> forms a dithiadiphosphetane disulfide.<ref>{{cite journal
 | |title = 2,4-Diferrocenyl-1,3-dithiadiphosphetane 2,4-disulfide; structure and reactions with catechols and [PtCl<sub>2</sub>(PR<sub>3</sub>)<sub>2</sub>](R = Et or Bun)
 | |author = Mark R. St. J. Foreman, Alexandra M. Z. Slawin and J. Derek Woollins
 | |journal = J. Chem. Soc., Dalton Trans., 
 | |year = 1996
 | |pages =   3653 &ndash;– 3657
 | |doi = 10.1039/DT9960003653
}}</ref>

===Redox chemistry===
{{main|Ferrocenium}}
Unlike the majority of hydrocarbons, ferrocene undergoes a one-electron oxidation at a low potential, around 0.5 V ''vs''. a [[saturated calomel electrode]] (SCE). It is also been used as standard in electrochemistry as Fc+/Fc = 0.64 V vs. NHE. Some [[electron]] rich hydrocarbons (e.g., [[aniline]]) also are oxidized at low potentials, but only irreversibly. Oxidation of ferrocene gives a stable cation called ferrocenium. On a preparative scale, the oxidation is conveniently effected with FeCl<sub>3</sub> to give the blue-colored ion, [Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>]<sup>+</sup>, which is often isolated as its [[hexafluorophosphate|PF<sub>6</sub><sup>−</sup>]] salt. Alternatively, [[silver nitrate]] may be used as the oxidizer.

Ferrocenium salts are sometimes used as oxidizing agents, in part because the product ferrocene is fairly inert and readily separated from ionic products.<ref>{{cite journal|author=N. G. Connelly, W. E. Geiger| title=Chemical Redox Agents for Organometallic Chemistry|journal=[[Chemical Reviews]]|year= 1996| volume= 96| pages= 877–910| doi=10.1021/cr940053x}}</ref>   Substituents on the cyclopentadienyl ligands alters the redox potential in the expected way: electron withdrawing group such as a carboxylic acid shift the potential in the [[anodic]] direction (''i.e.'' made more positive), whereas electron releasing groups such as [[methyl]] groups shift the potential in the [[cathodic]] direction (more negative). Thus, decamethylferrocene is much more easy to oxidise than ferrocene itself. Ferrocene is often used as an [[internal standard]] for calib(contracted; show full)03>{{cite journal|author=S. Top, A. Vessières, G. Leclercq, J. Quivy, J. Tang, J. Vaissermann, M. Huché and G. Jaouen| title=Synthesis, Biochemical Properties and Molecular Modelling Studies of Organometallic Specific Estrogen Receptor Modulators (SERMs), the Ferrocifens and Hydroxyferrocifens: Evidence for an Antiproliferative Effect of Hydroxyferrocifens on both Hormone-Dependent and Hormone-Independent Breast Cancer Cell Lines| journal=Chemistry, a European Journal| year=2003| volume=9| pages=5223–36
 | |pmid=14613131 | |doi=10.1002/chem.200305024|issue=21}}</ref><ref>{{cite journal|journal=[[Chemical and Engineering News]] | |date=16 September 2002| title= The Bio Side of Organometallics | |author= Ron Dagani| volume = 80| issue= 37| pages = 23–29| url=http://pubs.acs.org/cen/science/8037/8037sci1.html}}</ref><ref>
{{cite journal|author=S. Top, B. Dauer, J. Vaissermann and G. Jaouen| journal=[[Journal of Organometallic Chemistry]]| title= Facile route to ferrocifen, 1-[4-(2-dimethylaminoethoxy)]-1-(phenyl-2-ferrocenyl-but-1-ene), first organometallic analogue of tamoxifen, by the McMurry reaction | |doi=10.1016/S0022-328X(97)00086-7 |year=1997| volume=541| pages= 355–361}}</ref>

===Materials chemistry===
Ferrocene, being readily sublimed, can be used to deposit certain kinds of fullerenes, especially carbon nanotubes. Due to the fact that many organic reactions can be used to modify ferrocenes, it is the case that [[vinyl]] ferrocene can be made. The vinyl ferrocene can be made by a [[Wittig reaction]] of the [[aldehyde]], a [[phosphonium salt]] and [[sodium hydroxide]].<ref>Liu, Wan-yi; X(contracted; show full)

==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.{{cite journal|doi=10.1016/S0020-1693(99)00123-1}}</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.{{cite journal|doi=10.1016/0022-328X(90)85359-7}}</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.{{cite journal|doi=10.1021/ic00133a006}}</ref>

Because of the ease of substitution, many structurally unusual ferrocene derivatives have been prepared. For example, the penta(ferrocenyl)cyclopentadienyl ligand,<ref>{{cite journal|author=Y. Yu, A.D. Bond, P. W. Leonard, K. P. C. Vollhardt, G. D. Whitener| title=Syntheses, Structures, and Reactivity of Radial Oligocyclopentadienyl Metal Complexes: Penta(ferrocenyl)cyclopentadienyl and Congeners| journal= [[Angewandte Chemie International Edition]]| volume =45 | |issue=11| pages= 1794–1799|year=2006| doi=10.1002/anie.200504047}}</ref> features a cyclopentadiene derivatised with five ferrocene substituents.

[[Image:Penta(ferrocenyl)cyclopentadienyl.png|500px|center|Penta(ferrocenyl)cyclopentadienyl ligand]]

[[Image:Hexaferrocenylbenzene-3D-sticks.png|200px|thumb|right|Structure of hexaferrocenylbenzene]]

In '''hexaferrocenylbenzene''', all six positions on a [[benzene]] molecule have ferrocenyl substituents ('''R''').<ref>{{cite journal|title=Hexaferrocenylbenzene|author= Yong Yu, Andrew D. Bond, Philip W. Leonard, Ulrich J. Lorenz, Tatiana V. Timofeeva, K. Peter C. Vollhardt, Glenn D. Whitener and Andrey A. Yakovenko| journal=[[Chemical Communications]]| year=2006| pages= 2572–2574 |doi=10.1039/b604844g}}</ref> [[X-ray diffraction]] analysis of this compound confirms that the cyclopentadienyl ligands are not co-planar with the benzene core but have alternating [[dihedral angle]]s of +30° and −80°. Due to steric crowding the ferrocenyls are slightly bent with angles of 177° and have elongated C-Fe bonds. The quaternary cyclopentadienyl carbon atoms are also [[pyramidalization|pyramidalized]].<ref>Also, the benzene core has a [[chair conformation]] with dihedral angles of 14° and displays [[bond length]] alternation between 142.7 [[picometer|pm]] and 141.1 pm, both indications of steric crowding of the substituents.</ref>

<br {{clear = all/>}}

==References==
{{reflist|2}}

{{commonscat|ferrocene}}

==Further reading==
;Announcement of the discovery of ferrocene, but with wrong structure
*{{cite journal|author=Kealy, T. J., Pauson, P. L.|title=A New Type of Organo-iron Compound|journal= [[Nature (journal)|Nature]]| year= 1951 | |volume= 168| pages =1039–40 | |doi = 10.1038/1681039b0}}
*  {{cite journal| author=Miller, S. A., Tebboth, J. A., Tremaine, J. F.|journal= [[Journal of the Chemical Society]] | |year=1952| pages= 632–635| title=114. Dicyclopentadienyliron |doi=10.1039/JR9520000632}}
;Announcement of the correct 'sandwich' structure
*{{cite journal|author=[[Geoffrey Wilkinson|Wilkinson, G.]], Rosenblum, M., Whiting, M. C., [[Robert Burns Woodward|Woodward, R. B.]]|title= The Structure of Iron Bis-Cyclopentadienyl| journal=[[Journal of the American Chemical Society]]|year= 1952| volume=74|pages=2125–2126 | |doi = 10.1021/ja01128a527}}
*{{cite journal |author=Fischer, E. O., Pfab, W.|title=Cyclopentadien-Metallkomplexe, ein neuer typ metallorganischer Verbindungen |journal=[[Zeitschrift für Naturforschung B]]|year=1952| volume=7 |pages=377–379}}
;Others
*{{cite journal|author=Dunitz, J. D., Orgel, L. E.|title=Bis-Cyclopentadienyl - A Molecular Sandwich|journal= [[Nature (journal)|Nature]] |year=1953| volume=171 |pages= 121–122 | |doi = 10.1038/171121a0}}
*{{cite journal|author=Pauson, P. L.|title=Ferrocene-how it all began|journal=[[Journal of Organometallic Chemistry]]|year=2001|pages=637–639 | |volume = 637-639 | |doi = 10.1016/S0022-328X(01)01126-3}}
*{{cite book|author= Gerard Jaouen (ed.)| title=Bioorganometallics: Biomolecules, Labeling, Medicine| publisher=Wiley-VCH| location= Weinheim| year= 2006 | |isbn=978-3-527-30990-0}} (discussion of biological role of ferrocene and related compounds)

[[Category:Iron compounds]]
[[Category:Metallocenes]]
[[Category:Antiknock agents]]
[[Category:Sandwich compounds]]

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