The reaction of Bi, Pt and BiX₃ (X = Cl, Br) in an inert flux of AlX₃ yields black crystals of the subhalides PtBi₆X ₁₀. The compounds can also be obtained from the cluster salts Bi ₂₃[PtBi₆ X₁₂] by abstracting 23 equivalents of BiX₃. Consequently, the formation of PtBi₆X₁₀ is favored at higher temperatures when the vapor pressure p(BiX₃) evolved from Bi_2/3[PtBi₆ X₁₂] is high. In accordance with the experimental results a quantitative thermo-dynamic description of the system Bi/Pt/Cl is given. X-ray diffraction on single-crystals at 293 K revealed that the two PtBi₆X₁₀ compounds crystallize isostructurally in the orthorhombic space group Pnma with a = 1631.4(1)/1682.39(5) pm, b = 2667.8(2)/ 2731.1(1) pm and c = 906.9(1)/978.30(4) pm for Z = Cl/Br. The fundamental motif of the structure is the cuboctahedral [PtBi₆X₁₂] cluster, in which the platinum atom centers an octahedron of bismuth atoms whose edges are bridged by twelve halogen atoms. By sharing two halogen atoms with in each case the two neighbors the clusters are concatenated into a cis-trans chain ¹∞[PtBi₆X₈X₄₂]. Despite the high metal content and their polymeric character, the compounds are semi-conducting since all valence electrons are localized in the electron precise clusters.