A triclinic polymorph of bis(μ2-ethanethiolato)-1:2κ2S:S;3:4κ2S:S-(μ4-disulfido-1:2:3:4κ4S:S:S′:S′)tetrakis[tricarbonyliron(II)](2 Fe—Fe)

Next to the monoclinic polymorph [Cheng et al. (2005). Acta Cryst. E61, m892–m894], the triclinic title compound, [Fe4(C2H5S)2(S2)(CO)12], is the second known form of this composition. The structure is composed of an [Fe2(C2H5S)(S)(CO)6] subcluster, which is linked to its counterpart by an inversion centre located at the mid-point of the central disulfide bond. The Fe2S2 core of each subcluster exhibits a butterfly-like shape, with two S atoms bridging two Fe atoms. In the subcluster, each Fe atom is coordinated in a distorted octahedral coordination by three terminal carbonyl C atoms, two S atoms and one Fe atom. The crystal packing is accomplished through van der Waals interactions.