BI34IR3BR37 - A PSEUDO-SYMMETRICAL SUBBRO MIDE WITH BI-5(-6(2+) POLYCATIONS, AND [IRBI6BR12](-) AND [IRBI6BR13](2-) CLUSTER ANIONS() AND BI)

The melting reaction of Ir with Bi and BiBr3 yields black, lustrous, a ir insensitive crystals of the subbromide Bi34Ir3Br37. The triclinic c rystal structure (space group P1, a = b = 1303.4(2) pm, c = 1647.4(4) pm, alpha = beta 90 degrees, gamma = 120 degrees, V = 2423.7 x 10(6) p m(3)) deceives pseudo symmetry with respect to the rhombohedral space group <R(3)over bar>, which results in multiply twinned crystals. The structure can formally be subdivided in four new types of ionic groups : (a) cuboctahedral [IrBi6Br12](-) clusters, (b) [IrBi6Br13](2-) clust ers with an additional Br atom, (c) Bi-5(+) Square pyramids, and (d) d istorted Bi-6(2+) octahedra. The compound shows a range of homogeneity due to variable contributions of the different clusters.