Stabilization of homonuclear Bi5+ and Bi62+ polycations by cluster anions in the crystal structures of Bi12-xIrCl13-x, Bi12-xRhCl13-x and Bi12-xRhBr13-x

The melting reaction of Bi with Rh or Ir and BiCl3 or BiBr3 yields black, metallic lustrous, air insensitive crystals of the subhalides Bi12-xMX13, (x)(M = Rh, Ir; X = Cl, Br; x < 1). The compounds have the same structural principle as the previously reported subbromide Bi34Ir3Br37. The structures can be subdivided in four types of complex ionic groups: cuboctahedral [MBi6X12](-) clusters, [MBi6X13](2-) clusters with an additional halide ion, Bi-5(+) square pyramids and distorted Bi-6(2+) octahedra. The range of homogeneity is due to variable contributions of the different clusters. Bi12-xIrCl13-x is a semiconductor with an extended extrinsic regime below 200 K and a band gap of about 0.4 eV at room temperature. The subchlorides are diamagnetic at room temperature though a paramagnetic contribution appears towards lower temperature. Below 40 K, both compounds pass through a magnetic ordering that shows a hysteresis curve in the magnetization. (C) 2002 Elsevier Science Ltd. All rights reserved.