Spontaneous reduction of mixed 2,2′-bipyridine/methylamine/chloro complexes of PtIV in water in the presence of light is accompanied by complex isomerization, loss of methylamine, and formation of a strong oxidant, presumably HOCl

Three 2,2'-bipyridine (2,2'-bpy) complexes of Pt-IV have been synthesized, characterized by X-ray crystallography, and their solution behavior in D2O studied by H-1 NMR spectroscopic analysis: mer-[PtCl3(2,2'-bpy)(MeNH2)]Cl center dot H2O (4), trans- [PtCl2 (2,2'-bpy)(MeNH2)(2)]Cl (5), and trans-[Pt (2,2'-bpy)(MeNH2)(2)(OH)(2)]Cl-2 (6; MeNH2=methylamine). Complexes 4 and 5 undergo hydrolysis of the Cl- ions, both in the dark and daylight, as evident from a drop in the pH value. Two solvolysis products were detected in the case of 4, which is indicative of species with equatorial and axial OH- groups. ne hydrolysis reaction of 5 implies that an axial Cl- group is replaced by an OH- moiety; in contrast, 6 remains virtually unaffected. Ordinary daylight, in particular irradiation with a 50-W halogen lamp, initially causes ligand-isomerization processes, which are followed by the reduction of 4 and 5 to Ptu species. This reduction of 4 and 5 is accompanied by the formation of hypochlorous acid, as demonstrated qualitatively in the decoloration test of indigo, and loss of MeNH2, which is particularly pronounced in the case of 5. The formation of Pt-II compounds is established on the basis of the J coupling constants of Pt-195 with selected H-1 NMR resonances. The results obtained herein are possibly also relevant to the chemistry of Cl-containing Pt-IV antitumor agents and their reactions with DNA.