The anions [Pt₂X₆(SMe₂)]^2–(X = Cl and Br), in which SMe₂ is the sole bridging group, and the anions [Pt₂X₅(SMe₂)]^– containing both a SMe₂ bridge and a halide bridge have been characterised as their [Prⁿ₄N] salts. Their ¹H n.m.r. and vibrational spectra are reported and assigned. ¹H N.m.r. and ¹H {¹⁹⁵Pt} INDOR spectroscopy are used to identify [Pt₂Cl₅(SMe₂)₂]^– as a product of the reaction of [PPh₄]Cl with Pt₂Cl₄(SMe₂)₂. The vibrational spectra of Pt₂X₄(SMe₂)₂(X = Cl or Br) are assigned on the basis of a sulphur-bridged structure but it is proposed that the analogous iodide is halide bridged. The sulphur-bridged anion [Pt₂Cl₅SMePh]^– has been prepared but Pt₂X₄(SPh₂)₂ are halide bridged. Two cis-[PtCl₂SMe₂] groups linked by a single bridging SMe₂ is postulated as the structure of Pt₂Cl₄(SMe₂)₃. Bands in the infrared spectrum of the benzene insoluble form of PtBr₂(SMe₂)₂ are shown to be due to the impurity cis-PtBr₂Me₂SO·SMe₂ rather than bridging SMe₂. The significance of bridging dimethyl sulphide is discussed in the light of the chemical and spectroscopic results.