thiolates

Thiolates are the conjugate bases of thiols (R–SH). In solution they exist predominantly as RS− paired with counterions such as Na+, K+, or Li+. They are typically formed by deprotonation of thiols with bases such as hydroxide, alkoxides, or stronger reagents like sodium hydride or amide bases.

Sulfur in thiolates is a soft, highly polarizable donor atom, which makes RS− a strong nucleophile and a good soft ligand for many metal centers. The acidity of the parent thiol influences thiolate formation: aliphatic thiols have pKa values around 10, while aryl thiols are more acidic and form thiolate under milder conditions.

Thiolate anions readily participate in carbon–sulfur bond formation, for example by reacting with alkyl halides to give thioethers. They can also undergo oxidation to form disulfides (RSSR). In coordination chemistry they bind to transition metals as sulfur donors, often stabilizing metal complexes; in biology, cysteine residues can deprotonate to thiolates and coordinate metals or participate in redox chemistry.

Due to their reactivity, thiolates are widely used as nucleophiles in organic synthesis and as ligands in organometallic and bioinorganic chemistry. They play important roles in synthesis, catalysis, and the function of metal-containing enzymes and materials.