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IUPAC name
3D model (JSmol)
  • InChI=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;;
  • [c1cccc1]-[Fe]-[c2cccc23].[c13cccc1]-[Fe]-[c2cccc2]
Molar mass 370.054 g·mol−1
Appearance dark orange solid
Melting point 239–240 °C (462–464 °F; 512–513 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Biferrocene is the organometallic compound with the formula [(C5H5)Fe(C5H4)]2. 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.[1] Its one-electron oxidized derivative [(C5H5)Fe(C5H4)]2+ attracted attention as a prototypical mixed-valence compound.[2]

A related compound is biferrocenylene, [Fe(C5H4)2]2 wherein all cyclopentadienyl rings are coupled. Formally, biferrocene is derived from one fulvalene ligand, and biferrocenylene is derived from two.


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.[2]


Aminophosphine ligands with biferroceno substituents have been prepared as catalysts for asymmetric allylic substitution[3] and asymmetric hydrogenation of alkenes.[4]

Related compounds[edit]


  1. ^ M. D. Rausch (1961). "Ferrocene and Related Organometallic π-Complexes. IV. Some Ullmann Reactions of Haloferrocenes". J. Org. Chem. 26 (6): 1802–1805. doi:10.1021/jo01065a026.
  2. ^ a b Cowan, D. O.; LeVanda, C.; Park, J.; Kaufman, F. (1973). "Organic Solid State. VIII. Mixed-Valence Ferrocene Chemistry". Acc. Chem. Res. 6: 1–7. doi:10.1021/ar50061a001.{{cite journal}}: CS1 maint: uses authors parameter (link)
  3. ^ Xiao, Li; Weissensteiner, Walter; Mereiter, Kurt; Widhalm, Michael (2002-03-08). "Novel Chiral Biferrocene Ligands for Palladium-Catalyzed Allylic Substitution Reactions". The Journal of Organic Chemistry. 67 (7): 2206–2214. doi:10.1021/jo016249w. ISSN 0022-3263. PMID 11925230.
  4. ^ Zirakzadeh, Afrooz; Groß, Manuela A.; Wang, Yaping; Mereiter, Kurt; Weissensteiner, Walter (2014-04-09). "Walphos versus Biferrocene-Based Walphos Analogues in the Asymmetric Hydrogenation of Alkenes and Ketones". Organometallics. 33 (8): 1945–1952. doi:10.1021/om401074a. ISSN 0276-7333. PMC 4006446. PMID 24795493.