A Structural Model for Mononuclear Fe(II) Alkyl Persulfide Intermediates and its Sulfide Release Chemistry

The interactions between persulfides (RSS – ) and mononuclear Fe II centers pervade biology and play central roles in both sulfide metabolism and the assembly of ubiquitous iron sulfur (Fe–S) clusters. Despite this prevalence, efforts to understand and characterize mononuclear Fe II alkyl persulfides are hampered by their general instability and the synthetic inaccessibility of persulfide synthons. We report the synthesis, characterization, and reactivity of the first synthetic mononuclear Fe II alkyl persulfide species with a biologically relevant coordination environment by using a combination of a sterically hindered contact-ion stabilized alkyl persulfide synthon and a sterically encumbered FeII precursor. Reduction of the isolated Fe II -SSR complex by either a thiol (DTT) or outer sphere (Cp* 2 Co) reductants leads to sulfide release akin to the reactivity proposed for Fe II alkyl persulfide intermediates in Fe–S cluster assembly enzymes.