Ferrole

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.^[3][4]

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

Some ferroles react with tertiary phosphines to give the substituted flyover complex Fe₂(CO)₅(PR₃)(C₄R₄CO).^[5][6]