As part of our interest in the synthesis and catalytic applications of chiral (diphenylphosphanyl)ferrocene ligands, we designed a number of P,N-containing ligands for use in asymmetric transfer hydrogenation (ATH). During the synthetic procedure to obtainrac-1-[(N,4-dimethylbenzenesulfonamido)methyl]-2-(diphenylphosphanyl)ferrocene, the title compound, [Fe(C5H5)(C26H25NO2PS)]0.55·[Fe(C5H5)(C26H25NO3PS)]0.45, was obtained as a by-product. It is composed of a ferrocene group disubstituted by a partially oxidized diphenylphosphanyl group, as confirmed by31P NMR analysis, and an (N,4-dimethylbenzenesulfonamido)methyl substituent. Owing to the partially oxidized diphenylphosphanyl group, it is best to view the crystal as being composed of a mixture of non-oxidized and oxidized phosphane, so it can be regarded as a cocrystal. It is also a racemate. To the best of our knowledge, the P=O distance [1.344 (4) Å] is the shortest observed for related (diphenylphosphoryl)ferrocene compounds. The packing is stabilized by weak C—H...O interactions, formingR22(10) hydrogen-bonding motifs, which build up a chain along thecaxis.