The vibrational spectra and structures of phosphorus compounds—I. Diphosphine disulfides

The infrared spectra of nine diphosphine disulfides, R₂P(S)P(S)R₂, have been recorded in the 250–1200 cm⁻¹ range both in solution and in the solid state. Some Raman data is reported for the tetramethyl, tetra(ethyl), and tetra(n-butyl) compounds. The most satisfactory interpretation of the data is that all the compounds exist in the trans (C_2h) conformation of the diphosphine disulfide structure in the solid state. The PS antisymmetric stretching frequency was found to have a similar dependency on the nature of the substituents to that reported for tertiary phosphine sulfides. The infrared spectrum of tetraphenyldiphosphine is also reported.