The title compound, [Co(C5H5)(C5H4O3S)], was synthesized by dediazoniation of cobaltoceniumdiazonium bis(hexafluoridophosphate) with CuCl and SO2, crystallizing as yellow platelets. Structurally, a regular cobaltocenium sandwich moiety is observed containing coplanar cyclopentadienyl rings and displaying unexceptional carbon–cobalt [2.0230 (16)–2.0452 (14) Å] and carbon–carbon [1.410 (3)–1.431 (3) Å] bond distances. In this mesoionic molecule, the cationic cobaltoceniumyl part is connected to its anionic sulfonate part by a carbon–sulfur single bond of 1.7717 (15) Å.
