A template-directed synthetic approach to halogen-bridged mixed-valence platinum complexes has been performed in organic media using, for instance, a syntheticpeptide bearing two bis(ethylenediamine)-based Pt(IV) complexes with two axial bromide anionic ligands, [(Pt(IV)Br2(en))2](RSO3)4, and a [Pt(II)(en)2](RSO3)2 complex (R = (C12H25OCH2)2CHO(CH2)3-).