AbstractThe reaction of [Cp(*)2Ru2‐(CO)4] [a: Cp(*)= Cp*(η5‐C5Me5);b: Cp(*)= Cpx(η5‐C5Me4Et)] with β‐realgar in boilingn‐decane gives [Cp(*)2Ru2‐As4S4] (1a,b). in good yields along with some [Cp(*)2Ru2‐As4S2] (2a,b). According to X‐ray diffraction analyses of1band2a, their structures belong to two different types of inorganic clusters. Whereas1bhas a cage structure in which the [Cp(*)2Ru2unit is inserted into the As4S4] cradle,2ahas a sandwich structure in which two coplanar η2‐As4S ligands and the Cp*ligands are oriented parallel to one another. Analysis of the As‐S connectivity in the core of1 breveals a structural relationship to the extremely rare form of arsenic sulfide As4S4(II), and not to the metastable high‐temperature form β‐As4S4used in the synthesis. At lower temperatures (60, 115°C) formation of CO‐