Oxidation of the acetate-bridged half-lantern platinum(II) complex cis-[Pt-II(NH3)(2)(mu-OAc)(2)Pt-II(NH3)(2)](NO3)(2), [1](NO3)(2), with iodobenzene dichloride or bromine generates the halide-capped platinum(III) species cis-[XPtIII(NH3)(2)(mu-OAc)(2)Pt-III(NH3)(2)X](NO3)(2), where X is Cl in [2](NO3)(2) or Br in [3](NO3)(2), respectively. These three complexes, characterized structurally by X-ray crystallography, feature short (approximate to 2.6 angstrom) Pt-Pt separations, consistent with formation of a formal metal-metal bond upon oxidation. Elongated axial Pt-X distances occur, reflecting the strong trans influence of the metal metal bond. The three structures are compared to those of other known dinuclear platinum complexes. A combination of H-1, C-13, N-14, and Pt-195 NMR spectroscopy was used to characterize [1](2+)-[3](2+) in solution. All resonances shift downfield upon oxidation of [1](2+) to [2](2+) and [3](2+). For the platinum(III) complexes, the N-14 and Pt-195 resonances exhibit decreased line widths by comparison to those of [1](2+). Density functional theory calculations suggest that the decrease in the N-14 line width arises from a diminished electric field gradient at the N-14 nuclei in the higher valent compounds. The oxidation of [1](NO3)(2) with the alternative oxidizing agent bis(trifluoroacetoxy)iodobenzene affords the novel tetranuclear complex cis-[(O2CCF3)Pt-III(NH3)(2)(mu-OAc)(2)Pt-III(NH3)(mu-NH2)](2)(NO3)(4), [4](NO3)(4), also characterized structurally by X-ray crystallography. In solution, this complex exists as a mixture of species, the identities of which are proposed.