In organoiron chemistry, a ferrole is a type of diiron complex containing the (OC)<sub>3</sub>FeC<sub>4</sub>R<sub>4</sub> heterocycle that is pi-bonded to a Fe(CO)<sub>3</sub> group. These compounds have Fe-Fe bonds (ca. 252 pm) and semi-bridging CO ligands (Fe-C distances = 178, 251 pm). They are typically air-stable, soluble in nonpolar solvents, and red-orange in color.
Ferroles typically arise by the reaction of alkynes with iron carbonyls. Such reactions are known to generate many products, e.g. complexes of cyclopentadienones and para-quinones.
Another route involves the desulfurization of thiophenes (SC<sub>4</sub>R<sub>4</sub>) by iron carbonyls, shown in the following idealized equation:
An unusual route to ferroles involves treatment of Collman's reagent with trimethylsilyl chloride (tms = (CH<sub>3</sub>)<sub>3</sub>Si):
Some ferroles react with tertiary phosphines to give the substituted flyover complex Fe<sub>2</sub>(CO)<sub>5</sub>(PR<sub>3</sub>)(C<sub>4</sub>R<sub>4</sub>CO).