The cluster [Fe2S2(SBut)(4)](2-) on reacting with L-cysteine ethyl est
er hydrochloride (HCys-OEt . HCl) converts to the tetranuclear cystein
ate-bound cluster [Fe4S4(Cys-OEt . HCl)(4)](2-). In contrast, the dinu
clear tyrosinate-bound cluster, [Fe2S2(Tyr-OMe)(4)](2- (HTyr-OMe-L-tyr
osine methyl ester) can be prepared from either [Fe2S2(SBut)(4)](2-) o
r [Fe2S2Cl4](2-), or as a decomposition product in the reaction of hex
anuclear [Fe6S6Cl6](3-) with NaTyr-OMe. Under appropriate conditions t
he hexanuclear tyrosinate-bound cluster [Fe6S6(Tyr-OMe)(6)](3-) can be
isolated. The thermal stability of clusters [Fe6S6(XR)(6)](3-) (X=S,
O) toward conversion to tetranuclear [(FeS4)-S-4(XR)(4)](2-) lies in t
he order tyrosinate- greater than or equal to phenolate- > thiophenola
te-bound duster. H-1 NMR and Mossbauer spectroscopies are used to uneq
uivocally identify the products.