ironthiolate

Iron thiolate refers to chemical species in which iron is coordinated by thiolate ligands, RS−, derived from deprotonated thiols. The term covers discrete molecular complexes as well as thiolate-containing motifs found in certain iron enzymes. Thiolate ligands are soft, strong σ-donors, and their presence can influence the oxidation state, geometry, and reactivity of the iron center, often favoring four- to six-coordinate environments and enabling unusual or reactive electronic structures.

In synthetic chemistry, iron–thiolate complexes are prepared by binding thiolate ligands to iron in various oxidation states, commonly Fe(II) or Fe(III). These complexes may feature mononuclear or polynuclear arrangements and can include bridging RS− ligands. The Fe–S bonds created by thiolate ligation can stabilize high or low oxidation states and affect reactivity toward small molecules, such as oxygen or hydrocarbons. Spectroscopic techniques, including UV–visible, infrared (for Fe–S stretches), Mössbauer spectroscopy, and X-ray crystallography, are used to characterize these systems.

Biologically, iron–thiolate motifs are notable in heme-thiolate enzymes, such as cytochrome P450, where a cysteine thiolate acts as the axial ligand to a heme iron and modulates reactivity. Non-heme iron proteins may also employ cysteine or other thiolate donors to tune coordination geometry and catalytic function. The study of iron thiolates provides model systems for understanding how sulfur-donor ligands influence iron chemistry and mechanisms in both synthetic and biological contexts. See also iron–sulfur chemistry, heme-thiolate, and cysteine ligation.