Sulfurbridged

Sulfur-bridged refers to a structural motif in which sulfur atoms serve as bridges that connect two parts of a molecule, a metal center, or two fragments of a cluster. In inorganic and organometallic chemistry, sulfur bridges most often take the form of μ-S ligands (sulfide, S2−) or multisulfur linkages that connect two metal centers, producing di- or polynuclear complexes. A common variant is the μ2-sulfide bridge, where a single sulfur atom links two metals, while μ3- or μ4-sulfide bridges connect three or four centers within a cluster. Sulfur can also link organic fragments as thioether bridges (−S−) or form disulfide bridges (−S−S−) between parts of a molecule.

Occurrences and significance: Sulfur-bridged motifs are widespread in metal-sulfur clusters, including tetra- or octa-nuclear clusters, as well as in biological systems such as iron-sulfur clusters and hydrogenase active sites that feature sulfur ligation. The sulfur bridges influence the electronic structure, redox properties, and magnetic coupling between centers, and they enable pathways for electron transfer and catalysis.

Preparation and analysis: Sulfur bridges are typically introduced during the self-assembly of metal-sulfur clusters from sulfide sources and metal precursors, or by sulfidation of sulfur-containing ligands. They are characterized by X-ray crystallography, vibrational spectroscopy (IR/Raman for M–S vibrations), and, when applicable, Mössbauer spectroscopy or EPR to probe oxidation states.

Applications: In bioinorganic modeling, catalysis, and materials science, sulfur-bridged motifs provide structural motifs and electronic communication essential for reactivity and function.