BI12NI4I3 - A SUBIODIDE OF THE INTERMETAL LIC PHASE BI3NI

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 in termetallic phase Bi3Ni. These fragments are chains consisting of face -sharing mono-capped trigonal prisms of bismuth atoms. Each prism is c entered by a nickel atom. The chains form porous layers which are fill ed and separated by iodine atoms. The iodine atoms show high coordinat ion numbers of eight and ten, respectively. The oxidation of Bi3Ni to Bi12Ni4I3 causes the interatomic distances within the chains to decrea se while the distance between them is increased. Extended Huckel calcu lations demonstrate that the variation of interatomic distances is dir ectly correlated to the bonding character of the energy levels that ar e emptied on introduction of iodine.