Difference between revisions 6001667 and 6001668 on simplewiki

{{chembox
| verifiedrevid = 396489042
| ImageFileL1 = Ferrocene.svg
| ImageSizeL1 = 80 px
| ImageFileR1 = Ferrocene-from-xtal-3D-balls.png
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| ImageFile2 = Photo of Ferrocene (powdered).JPG
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(contracted; show full)nyl 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|doi = 10.1002/chin.200443242|title = Ferrocene: 50 Years of Transition Metal Organometallic Chemistry — From Organic and Inorganic to Supramolecular Chemistry|year = 2004|last1 = Federman Neto|first1 = Alberto|last2 = Pelegrino|first2 = Alessandra Caramori|last3 = Darin|first3 = Vitor Andre|journal = ChemInform|volume = 35
|issue = 43}}</ref> The rapid growth of [[organometallic chemistry]] is often attributed to the excitement arising from the discovery of ferrocene and its many [[Structural analog|analogue]]s.

==History==
[[File:Ferrocene kealy.svg|thumb|left|Pauson and Kealy's original (incorrect) notion of ferrocene's molecular structure<ref name = "Pauson_Kealy" />]]
(contracted; show full)

[[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
 |issue = 8}}</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 = Zeitschrift für Naturforschung B |year = 1952 |volume = 7 |pages = 377–379 |doi =}}</ref><ref>A third group independently determined the structure of ferrocene.  See:  P. F. Eiland and R. Pepinsky (1952) "X-ray examination of iron biscyclopentadienyl," ''Journal of the American Chemical Society'', vol. 74, page 4971.  See also:  Pierre Laszlo and Roald Hoffmann (2000) "[http://www.roaldhoffmann.com/pn/modules/Downloads/docs/Ferrocene.pdf Ferrocene:  Ironclad History of Rashomon Tale?]," ''Angewandte Chemie'' (International Edition), vol. 39, no. 1, pages 123-124.</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 = 373–375 |doi = 10.1107/S0365110X56001091 |issue = 4}}</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 o(contracted; show full)

Numerous other syntheses have been reported, including the direct reaction of [[gas]]-phase cyclopentadiene with metallic iron<ref>{{cite journal|doi=10.1021/ja01636a080|year=1954|last1=Wilkinson|first1=G.|authorlink1=Geoffrey Wilkinson|last2=Pauson|first2=P. L.|last3=Cotton|first3=F. A.|journal=[[J. Am. Chem. Soc.]]|volume=76|pages=1970
|issue=7}}</ref> at 350 °C or with [[iron pentacarbonyl]].<ref>{{cite journal|doi=10.1002/9780470166024.ch1|year=1959|last1=Wilkinson|first1=G.|authorlink1=Geoffrey Wilkinson|last2=Cotton|first2=F. A.|title=Cyclopentadienyl and Arene Metal Compounds|journal=Progress in Inorganic Chemistry|volume=1|pages=1–124}}</ref>
[[Image:Ferrocene 3d model 2.png|thumb|right|A space-filling model of the [[staggered conformation]] of ferrocene.]]

(contracted; show full)

Direct transmetalation can also be used to prepare ferrocene from other metallocenes, such as [[manganocene]]:<ref>{{cite journal |last1= Wilkinson|first1= G.|authorlink1= Geoffrey Wilkinson|last2= Cotton|first2= F. A.|last3= Birmingham|first3= J. M.|year= 1956|title= On manganese cyclopentadienide and some chemical reactions of neutral bis-cyclopentadienyl metal compounds|journal= J. Inorg. Nucl. Chem.|volume= 2|issue= 
2|pages= 95|url= |doi=10.1016/0022-1902(56)80004-3 }}</ref>

:FeCl<sub>2</sub> + Mn(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> &rarr; MnCl<sub>2</sub> + Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>

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 (phase transition)|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>{{cite journal|doi=10.1021/je050502y|title=New Static Apparatus and Vapor Pressure of Reference Materials:  Naphthalene, Benzoic Acid, Benzophenone, and Ferrocene|year=2006|last1=Monte|first1=Manuel J. S.|last2=Santos|first2=Luís M. N. B. F.|last3=Fulem|first3=Michal|last4=Fonseca|first4=José M. S.|last5=Sousa|first5=Carlos A. D.|journal=Journal of Chemical & Engineering Data|volume=51|pages=757|issue=2}}</ref>

{| class="wikitable"
|-
! pressure(Pa)
! 1
! 10
! 100
(contracted; show full)038 }}</ref> whereas treatment with [[dichlorophenylphosphine|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 = 1090–1092 |doi = 10.1021/jo01039a055 
|issue = 4 }}</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 = 3653–3657 |doi = 10.1039/DT9960003653 |issue = 18}}</ref>

===Redox chemistry===
{{main|Ferrocenium}}
Unlike the majority of organic compounds, 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. SHE. Some [[electron]]-rich organic compounds (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| pmid=11848774|issue=2}}</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 [[Cathode|cathodic]] direction (more negative). Thus, [[decamethylferrocene]] is much more easily oxidised than ferrocene. Ferrocene is often used as an [[internal s(contracted; show full)chemical synthesis of azaferrocene|year=1990|last1=Zakrzewski|first1=J|journal=Journal of Organometallic Chemistry|volume=388|pages=175}}</ref> This compound on boiling under [[reflux]] in [[benzene]] is converted to ferrocene.<ref>{{cite journal|doi=10.1021/ic00133a006|title=Chemistry of some .eta.5-pyrrolyl- and .eta.1-N-pyrrolyliron complexes |year=1982 |last1=Efraty |first1=Avi. |last2=Jubran |first2=Nusrallah |last3=Goldman |first3=Alexander |journal=Inorganic Chemistry|volume=21|pages=868
|issue=3}}</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= 1794–17(contracted; show full)
;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=[[J. Am. Chem. Soc.]]|year= 1952| volume=74|pages=2125–2126|doi = 10.1021/ja01128a527
|issue=8}}
*{{cite journal |author=[[Ernst Otto Fischer|Fischer, E. O.]], Pfab, W.|title=Cyclopentadien-Metallkomplexe, ein neuer typ metallorganischer Verbindungen |journal=Z. Naturforsch. 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|issue=4342}}
*{{cite journal|author=Pauson, P. L.|title=Ferrocene-how it all began|journal=[[Journal of Organometallic Chemistry|J. Organomet. Chem.]]|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)
*University of Nottingham Molecular Videos, [http://www.periodicvideos.com/videos/mv_ferrocene.htm "Ferrocene"]

[[Category:Organoiron compounds]]
[[Category:Metallocenes]]
[[Category:Antiknock agents]]
[[Category:Sandwich compounds]]
[[Category:Cyclopentadienyl complexes]]

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