Reaction of K-2[Pt((NO2)-N-15)(4)] under argon with 1 M HClO4 or CF3SO3H gave an initial blue solution (lambda(max) = 627 nm), due to nitrosyl complexes of platinum(IV), With heating, the color faded, and Pt-195 and N-15 NMR peaks were observed from cis-[Pt((NO2)-N-15)(2)(H2O)(2)], [Pt((NO2)-N-15)(H2O)(3)](+), and fac-[Pt((NO2)-N-15)(3)(H2O)(3)](+). In air of oxygen, reaction was faster, giving [Pt(H2O)(4)](2+) as well as mixed nitrito-N/aqua platinum(II) complexes, and larger proportions of platinum(IV) complexes, including [Pt(OH)(6)](2-) in solution, and solid H-2[Pt(OH)(6)]. With 0.5 M H2SO4. reactions were similar, but a greater variety of platinum(IV) complexes were formed, some probably containing coordinated sulfate. With 1 M HNO3, K-2[Pt(NO2)(6)] formed. Reactions of K-2[Pt(NO2)(4)] with aqueous acetic acid gave mixtures of Pt(II) and PI(IV) mononuclear complexes and dinuclear Pt(III) complexes containing acetate bridges. The composition of the solution depended on the reaction conditions (heated for various times with argon, air, or oxygen above the solution or bubbled through).Crystals of K-2[{Pt-II(NO2)(2)(mu-CH3CO2)}(2)]. H2O were obtained from a reaction under argon, and the crystal structure was determined by X-ray diffraction: space group P $(1) over bar$$ (no. 2); a = 7.202(2) Angstrom; b = 8.987(2) Angstrom; c = 13.592(2) Angstrom; alpha = 94.01(2)degrees; beta = 90.68(2)degrees; gamma = 111.04(2)degrees; Z = 2; R = 0.0371, for 2875 reflections. The structure showed two acetate ligands bridging between cis-Pt(NO2)(2) units, with the Pt-Pt distance 2.986(1) Angstrom. Reactions of cis-[Pt(NO2)(2)(H2O)(2)] with various oxidants in the presence of acetic acid were studied. [{(CH3CO2)Pt-III(NO2)(2)(mu-CH3CO2)}(2)](2-) is formed by the oxidation of preformed [{Pt-II(NO2)(2)(mu-CH3CO2)}(2)](2-). Under anaerobic conditions, the major oxidant is HNO3 formed in the reaction mixture. Oxidation of [{Pt-II(NO2)(2)(mu-CH3CO2)}(2)](2-) with NO2 formed in the reaction mixture in the presence of oxygen provides one route to [(O2N)Pt-III(NO2)(2)(mu-CH3CO2)(2)Pt-III(NO2)(2)(O2CCH3)](2-). Continued heating of solutions containing these Pt(III) complexes eventually gave solutions containing [{(CH3CO2)Pt-III(NO2)}(2)(mu CH3CO2)(3)](-).