[en] Recent studies of the oxidation-reduction reactions of platinum II and IV complexes have provided evidence for the transient existence of platinum complex ions in the unusual oxidation states of I and III. Only for monodentate ligands have the intermediates been observed and characterized. In this work, the techniques of pulse radiolysis and flash photolysis have been implemented, through the construction of suitable apparatus, to study the reactions of [PtCl₄]^2-, cis-[Pt(gly)₂], [Pt-(dien)Cl]⁺, [Pt(Et₄dien)Cl]⁺, [Pt(en)₂]²⁺, and trans-[Pt(en)₂Cl₂]²⁺ complex ions with e^-/sub aq/, .H, .OH, Cl^-₂, and iso-propanol radicals. The flash photolysis of trans-[Pt(en)₂Cl₂]²⁺ was investigated as an independent method of generating Pt(III) species. The Pt(III) transient species are proposed to be formed with essentially distorted octahedral structures, which are closely related via substitutional lability and acid-base reactions involving Cl^-, OH^-, and H₂O ligands. For the platinum-ethylenediamine systems, the general form of the Pt(III) species is suggested to be [Pt(en)₂(X)(Y)]/sup n+/, where X and Y are combinations of the chloro, hydroxo, and aquo ligands. The results of this study indicate that the complexation of simple amines and amino acids with platinum metal centers may offer a significant degree of radiation protection to the organic ligands