Ferrole
# Ferrole

In organoiron chemistry, a ferrole is a type of diiron complex containing the $(OC)_3FeC_4R_4$ 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 $(SC_4R_4)$ by iron carbonyls, shown in the following idealized equation:

    $Fe_3(CO)_{12}$ + $SC_4R_4$ → $Fe_2(CO)_6C_4R_4$ + FeS + 6 CO

An unusual route to ferroles involves treatment of Collman's reagent with trimethylsilyl chloride (tms = $(CH_3)_3Si):$

    2 $Na_2Fe(CO)_4$ + 4 tmsCl → $Fe_2(CO)_6C_4(Otms)_4$ + 2 CO + 4 NaCl

## Reactions

Some ferroles react with tertiary phosphines to give the substituted flyover complex $Fe_2(CO)_5(PR_3)(C_4R_4CO).$

