Reaction of K-2[Pt(NO2)(4)] With CH3CO2H/H2O/HA, where HA = HClO4, CF3SO3H, or HNO3, gave [{(H2O)Pt(mu-CH3CO2)(2)}(2)]A(2). With nitrite highly enriched in N-15, the reactions which led to these final products were followed by Pt-195 NMR, and intermediate platinum(III) complexes were identified. Crystal structures were determined by X-ray diffraction for the perchlorate and trifluoromethanesulfonate salts : for [{(H2O)Pt(mu-CH3CO2)(2)}(2)](ClO4)(2), monoclinic crystal system, space group P2(1)/c, a = 8.113(4) Angstrom, b = 8.279(2) Angstrom, c = 14.892(7) Angstrom, beta = 101.16(2)degrees, V = 981.4(7) Angstrom(3), Z = 2, Pt-Pt = 2.3906(13) Angstrom; for [{(H2O)Pt(mu-CH3CO2)(2)}(2)](CF3SO3)(2) . 4H(2)O, monoclinic crystal system, space group P2(1)/c, a = 8.162(2) Angstrom, b = 8.982(1) Angstrom, c = 19.404(6) Angstrom, beta = 95.51(1)degrees, V = 1416.0(5) Angstrom(3), Z = 2, Pt-Pt = 2.3929(6) Angstrom. In water, there was rapid conversion to a complex with three acetate bridges. In acetic acid or dmf, there was replacement of the axial water ligands by acetate or dmf, respectively, but the tetra-acetate-bridged structure remained intact for several hours. Some axially-substituted derivatives were obtained in solution by addition of ligands to a dmf solution of the trifluoromethanesulfonate salt and were characterized by Pt-195 NMR. Solids [{XPt(mu-CH3CO2)(2)}(2)] were isolated with X = Cl, Br. The crystal structures of [{(H2O)Pt(mu-CH3CO2)(2)}(2)]A(2) showed Pt-Pt-O(acetate) angles slightly less than 90 degrees. This, together with very low shielding of the carboxylate carbon nuclei in the tetra-acetate-bridged complexes, was interpreted as indicating strain in these structures. UV spectra of the compounds were similar to those of sulfate- and hydrogen phosphate-bridged platinum(III) complexes with the same axial ligands.