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Abstract:
Reaction of Bi with Pb, Pt and BiI3 above 330 degrees C yielded shiny, black, air insensitive crystals of the subiodide Pb[PtBi6I12]. Pb[PtBi6I12] crystallizes in the rhombohedral space group R3 with lattice parameters a = 1585.39(5) pm and c = 1098.77(3) pm at room temperature. The compound consists of cuboctahedral [PtBi6I12](2-) clusters and Pb2+ cations in octahedral coordination between trigonal faces of two cuboctahedra, which concatenate them into linear chains. Six weaker Bi center dot center dot center dot I inter-cluster bridges per cluster connect the chains. The structure can be interpreted as a superstructure of the NaCl structure type, with iodide and platinum(-II) as anions and bismuth(II) and lead(II) as cations, leaving 18 out of 39 cation positions unoccupied. The arrangement of the cuboctahedral clusters follows the motif of a body-centered cubic packing. Pb[PtBi6I12] is a semiconductor with a measured bandgap of 0.69 eV. Full-relativistic DFT calculations indicate a topologically trivial bandgap of 0.58 eV.
