{{short description|Organometallic compound}} {{Chembox | ImageFile = Biferrocene.svg | ImageSize = 122 | ImageAlt = | IUPACName = 1,1"-Biferrocene | OtherNames = |Section1={{Chembox Identifiers | CASNo = 1287-38-3 | PubChem = 11984633 | ChemSpiderID = 10157133 | SMILES = C1=C[CH-]C=C1.[Fe+2].C2=C[C-](C=C2)[C-](C=C3)C=C3.[Fe+2].C1=C[CH-]C=C1 | StdInChI=1S/C10H8.2C5H5.2Fe/c1-2-6-9(5-1)10-7-3-4-8-10;2*1-2-4-5-3-1;;/h1-8H;2*1-5H;;/q-6;2*-1;; | StdInChIKey = CEMHVYUXQJEPPO-UHFFFAOYSA-N }} |Section2={{Chembox Properties | C=20|H=18|Fe=2 | MolarMass = | Appearance = dark orange solid | Density = | MeltingPtC = 239-240 | BoilingPt = | Solubility = }} |Section3={{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }} '''Biferrocene''' is the organometallic compound with the formula [(C<sub>5</sub>H<sub>5</sub>)Fe(C<sub>5</sub>H<sub>4</sub>)]<sub>2</sub>. It is the product of the formal dehydrocoupling of ferrocene, analogous the relationship between biphenyl and benzene. It is an orange, air-stable solid that is soluble in nonpolar organic solvents.
Biferrocene can be prepared by the Ullmann coupling of iodoferrocene.<ref name=":0">{{cite journal|title= Ferrocene and Related Organometallic π-Complexes. IV. Some Ullmann Reactions of Haloferrocenes|author=M. D. Rausch|journal=J. Org. Chem.|year=1961|volume=26|issue=6|pages=1802–1805|doi=10.1021/jo01065a026}}</ref> Its one-electron oxidized derivative [(C<sub>5</sub>H<sub>5</sub>)Fe(C<sub>5</sub>H<sub>4</sub>)]<sub>2</sub><sup>+</sup> attracted attention as a prototypical mixed-valence compound.<ref name=":1">{{cite journal|author1=Cowan, D. O. |author2=LeVanda, C. |author3=Park, J. |author4=Kaufman, F. |title=Organic Solid State. VIII. Mixed-Valence Ferrocene Chemistry|journal=Acc. Chem. Res.|year=1973|volume=6|pages=1–7|doi=10.1021/ar50061a001}}</ref>
A related compound is biferrocenylene, [Fe(C<sub>5</sub>H<sub>4</sub>)<sub>2</sub>]<sub>2</sub> wherein all cyclopentadienyl rings are coupled into two fulvalene ligands.
== Reactions == Biferrocene can easily be converted into a mixed-valence complex, which is called biferrocenium. This [Fe(II)-Fe(III)] cation is a class II type (0.707 > α > 0) mixed-valence complex according to the Robin-Day classification.<ref name=":1" />
==Derivatives== Aminophosphine ligands with biferroceno substituents have been prepared as catalysts for asymmetric allylic substitution<ref>{{Cite journal |last1=Xiao |first1=Li |last2=Weissensteiner |first2=Walter |last3=Mereiter |first3=Kurt |last4=Widhalm |first4=Michael |date=2002-03-08 |title=Novel Chiral Biferrocene Ligands for Palladium-Catalyzed Allylic Substitution Reactions |url=http://dx.doi.org/10.1021/jo016249w |journal=The Journal of Organic Chemistry |volume=67 |issue=7 |pages=2206–2214 |doi=10.1021/jo016249w |pmid=11925230 |issn=0022-3263|url-access=subscription }}</ref> and asymmetric hydrogenation of alkenes.<ref>{{Cite journal |last1=Zirakzadeh |first1=Afrooz |last2=Groß |first2=Manuela A. |last3=Wang |first3=Yaping |last4=Mereiter |first4=Kurt |last5=Weissensteiner |first5=Walter |date=2014-04-09 |title=Walphos versus Biferrocene-Based Walphos Analogues in the Asymmetric Hydrogenation of Alkenes and Ketones |url=http://dx.doi.org/10.1021/om401074a |journal=Organometallics |volume=33 |issue=8 |pages=1945–1952 |doi=10.1021/om401074a |pmid=24795493 |pmc=4006446 |issn=0276-7333}}</ref>
== Related compounds == * Bis(fulvalene)diiron
==References== <references /> {{Cyclopentadienide complexes}} Category:Ferrocenes Category:Sandwich compounds Category:Cyclopentadienyl complexes