FeC5Me52

FeC5Me52, more commonly written as Fe(C5Me5)2, is an organometallic iron(II) complex in which the iron center is bound to two η5-pentamethylcyclopentadienyl (Cp*) ligands. The complex is a “sandwich” type structure in which the Fe(II) ion sits between two Cp* rings.

Electronic and structural features: Each Cp* ligand donates six electrons, giving a total of 12 electrons from ligands. With iron in the +2 oxidation state (d6), Fe(Cp*)2 is an 18-electron complex and typically diamagnetic. The geometry is a bent, two-ligand sandwich with the bulky Cp* rings imparting steric constraints that can influence reactivity and crystallinity. The methyl substituents increase solubility in organic solvents and can affect ligand–metal interactions compared with unsubstituted Cp.

Synthesis: A common preparation is a salt metathesis reaction of FeCl2 with two equivalents of sodium pentamethylcyclopentadienide (NaCp*): FeCl2 + 2 NaCp* → Fe(Cp*)2 + 2 NaCl, usually in THF under inert atmosphere. NaCp* is typically generated from Cp*H and NaH or prepared via base-mediated routes. Alternative routes use reductive approaches from FeCl2 or related precursors, but salt metathesis is a standard method.

Applications and handling: Fe(Cp*)2 serves as a versatile precursor for synthesizing other Cp*-containing iron complexes and related organometallic compounds. It is generally handled under inert conditions and in nonpolar solvents, with typical precautions for air- and moisture-sensitive organometallic reagents. Safety follows standard guidelines for iron-organometallics and organic solvents.

See also: cyclopentadienyl complexes, ferrocene, Cp* ligands, organometallic synthesis.