Cofnod E-bost: Bis[1,2-bis­(eth­oxy­carbon­yl)ethene-1,2-dithiol­ato-κ(2) S,S′]bis­(η(5)-penta­methyl­cyclo­penta­dien­yl)tetra-μ(3)-sulfido-diiron(IV)diiron(III)(3 Fe—Fe)