On the linear mixed valence compounds obtained by partial oxidation ofcis-diamminedichloroplatinum(II)

Summary The partial oxidation products ofcis-Pt(NH₃)₂Cl₂] (Cisplatin) by (NH₄)₂S₂O₈ and by K₂PtCl₆, as well as the recrystallization of the former product in various solutions (HClO₄, NaClO₄, NaBF₄, NaHSO₄, H₂SO₄) have been re-examined. Contrary to the conclusions of previous works, the general formulation of these compounds iscis-Pt²⁺(NH₃)₂Cl₂]X_x·yH₂O ( = 0.3–0.4, X = SO ₄ ^2– , PtCl ₄ ^2– , ClO ₄ ^2– , BF ₄ ^2– , HSO ₄ ^2– , ..., 0y 1). These materials are all linear chain Pt—Pt compounds belonging to the class III of Robin-Day compounds with Pt—Pt distances in the range 3.00–3.06 Å. The oxidation of Cisplatin by persulphate gives two sulphate compounds of the same formulation (x = 0.2), which differ in aspect, metallic character and spectral properties. Structural information was obtained from polarized micro-Raman spectra of a needle-like sample of the perchlorate and from X-ray powder diffraction spectra. The cell of the perchlorate was orthorhombic while the two sulphate forms had a monoclinic cell with slightly different parameters. Expansion of the Cisplatin interchain distance occurred only along one crystallographic direction. The two sulphate forms differed in the degree of order along this direction. An approximate structure is proposed and discussed in relation to the Cisplatin precursor.