A transition metal thiosulfate complex is a coordination complex containing one or more thiosulfate ligands. Thiosulfate occurs in nature and is used industrially, so its interactions with metal ions are of some practical interest. Three binding modes are common: monodentate (κ-), O,S-bidentate (κ-),and bridging (μ-). Typically, thiosulfate complexes are prepared from thiosulfate salts. In some cases, they arise by oxidation of polysulfido complexes, or by binding of sulfur trioxide to sulfido ligands.