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An orange-red crystalline solid, Fe(C5H5)2; m.p. 173°C. It can be made by adding the ionic compound Na+C5H5 (cyclopentadienyl sodium, made from sodium and cyclopentadiene) to iron(III) chloride. In ferrocene, the two rings are parallel, with the iron ion sandwiched between them (hence the name sandwich compound: see formula). The bonding is between pi orbitals on the rings and d-orbitals on the Fe2+ ion. The compound can undergo electrophilic substitution on the C5H5 rings (they have some aromatic character). It can also be oxidized to the blue ion (C5H5)2Fe+. Ferrocene is the first of a class of similar complexes called sandwich compounds. Its systematic name is di-π-cyclopentadienyl iron(II).


Subjects: Chemistry.

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