[Pt-3(mu-CO)(3)(PPh3)(3)] was prepared in high yield by the reaction of [Pt-3(mu-CO)(3)(PPh3)(4)] with H2O2. The carbonyl ligands in [Pt-3(mu-CO)(3)(PR3)(3)] (PR3 = PPh3, PPh(2)Bz, PCy3, P'Pr-3) may be completely replaced by sulfur dioxide to give [Pt-3(mu-SO2)(3)(PR3)(3)] or partially by one SO2 to give [Pt-3(mu-CO)(2)(mu-SO2)(PR3)(3)] (PR3 = PCy3 and (PPr3)-Pr-i). On the other hand, the addition of one molar equivalent of carbon monoxide to [Pt-3(mu-SO2)(3)(PR3)(3)] (PR3 = PCy3, (PPr3)-Pr-i) gave the complexes [Pt-3(mu-CO)(mu-SO2)(2)(PR3)(3)] Complete simulation of the C-13 NMR spectra could be achieved with the help of Pt-195 NMR data.