Biferrocene
Biferrocene is the organometallic compound with the formula 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. Its one-electron oxidized derivative 2+ attracted attention as a prototypical mixed-valence compound.
A related compound is biferrocenylene, 2 wherein all cyclopentadienyl rings are coupled into two fulvalene ligands.