Synthesis and structural characterization of sulfur rich iron (II) carbonyl dimers: Facile reversible reaction with carbon monoxide

The sulfur-rich iron carbonyl dimer complexes [Fe(CO)2(S′SiS2)]2 (2), and [Fe(CO)(S′SiS2)]2 (3) have been prepared. The [2Fe–2S] cores of the new complexes are planar. The binding mode of the tridentate sulfur ligand in complex 2 is facial with a S(thiolate)–Fe–S(thiolate) angle of 92°, while in complex 3, the S′SiS2 ligand binds the metal with a S(thiolate)–M–S(thiolate) angle of 120°. The Fe–Fe distance is reduced from 3.45 Å in complex 2 to 2.78 Å in the 32 electron dimer complex 3. Complexes 2 and 3 are at equilibrium in solution and can be readily interconverted by addition or removal of CO.