Ferrole

File:Fe2C4H4(CO)6 (FCPTCF).png

Structure of the ferrole Fe₂C₄H₄(CO)₆. Color scheme: red = O, gray = C, dark blue = Fe, white = H.

Not to be confused with Ferrule.

In organoiron chemistry, a ferrole is a type of diiron complex containing the (OC)₃FeC₄R₄ heterocycle that is pi-bonded to a Fe(CO)₃ 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.

Synthesis

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 (SC₄R₄) by iron carbonyls, shown in the following idealized equation:

Fe₃(CO)₁₂ + SC₄R₄ → Fe₂(CO)₆C₄R₄ + FeS + 6 CO

An unusual route to ferroles involves treatment of Collman's reagent with trimethylsilyl chloride (tms = (CH₃)₃Si):

2 Na₂Fe(CO)₄ + 4 tmsCl → Fe₂(CO)₆C₄(Otms)₄ + 2 CO + 4 NaCl

Reactions

Some ferroles react with tertiary phosphines to give the substituted flyover complex Fe₂(CO)₅(PR₃)(C₄R₄CO).