Crystal structure and magnetic properties of Bi(Bi9)[NbCl6]3, a new member of the structure family Bi(Bi9)[MX6]3, and the crystal structure of Bi8[Ta2O2Br7]2

Bi and Bi-III halides comproportionate to form subvalent cationic Bi clusters of various size and shape that can be stabilized in the solid state in the presence of suitable complex ions. Transition metal chlorides and bromides of group 4 elements lead to compounds of the Bi(Bi-9)[MX6](3) family, of which all members with M = Zr, Hf; X = Cl, Br are known. At 550 K Bi, BiCl3 and NbCl5, surprisingly, yield the isotypic Bi+(Bi-9(5+))([NbCl6](2-))(3) containing Nb-IV formed by reduction of Nb-V. The crystal structure [hexagonal; P6(3)/m, a = 1377.1(2), c = 1065.5(2) pm; Z = 2] contains Bi-9(5+) clusters, octahedral [NbCl6](2-) and disordered Bi+ ions. The low, temperature-dependent paramagnetic moment (76 K: 0.99 B.M.; 295 K: 1.22 B.M.) confirms the reduction of Nb to the +IV state. Bi-8[Ta2O2Br7](2), formed by a trace of H2O in a reaction of Bi, BiBr3 and TaBr5 at 570 K, adopts a new structure type [tetragonal; P4/mnc; a = 1448,0(1), c = 1830.6(2) pm; Z = 4] and consists of square-antiprismatic Bi-8(2+) clusters and one-dimensional polymeric bromooxotantalate(V) anions. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.