Bi₁₂Ni₄I₃ is obtained from the elements at 710 K. X-ray investigations using a single crystal (space group Cmcm, a = 406.54(7), b = 1581.2(3), c = 3455.0(6) pm) show the structure to contain fragments of the intermetallic phase Bi₃Ni. These fragments are chains consisting of face-sharing mono-capped trigonal prisms of bismuth atoms. Each prism is centered by a nickel atom. The chains form porous layers which are filled and separated by iodine atoms. The iodine atoms show high coord nation numbers of eight and ten, respectively. The oxidation of Bi₃Ni to Bi₁₂Ni₁I₃ causes the interatomic distances within the chains to decrease while the distance between them is increased. Extended Hückel calculations demonstrate that the variation of interatomic distances is directly correlated to the bonding character of the energy levels that are emptied on introduction of iodine.