Biferrocene

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

Names
IUPAC name 1,1"-Biferrocene
Identifiers
CAS Number	1287-38-3
3D model (JSmol)	Interactive image
ChemSpider	10157133
PubChem CID	11984633
InChI 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;; Key: CEMHVYUXQJEPPO-UHFFFAOYSA-N
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
Properties
Chemical formula	C20H18Fe2
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). Infobox references

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 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.^[2]

Derivatives

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

Related compounds

• Bis(fulvalene)diiron