Crystal Structure and Magnetic Properties of Bi(Bi 9 )[NbCl 6 ] 3 , a New Member of the Structure Family Bi(Bi 9 )[MX 6 ] 3 , and the Crystal Structure of Bi 8 [Ta 2 O 2 Br 7 ] 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 )[MX 6 ] 3 family, of which all members with M = Zr, Hf; X = Cl, Br are known. At 550 K Bi, BiCl 3 and NbCl 5 , surprisingly, yield the isotypic Bi + (Bi 9 5+ )([NbCl 6 ] 2− ) 3 containing Nb IV formed by reduction of Nb V . The crystal structure [hexagonal; P 6 3 / m ; a = 1377.1(2), c = 1065.5(2) pm; Z = 2] contains Bi 9 5+ clusters, octahedral [NbCl 6 ] 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 [Ta 2 O 2 Br 7 ] 2 , formed by a trace of H 2 O in a reaction of Bi, BiBr 3 and TaBr 5 at 570 K, adopts a new structure type [tetragonal; P 4/ mnc ; a = 1448.0(1), c = 1830.6(2) pm; Z = 4] and consists of square‐antiprismatic Bi 8 2+ clusters and onedimensional polymeric bromooxotantalate( V ) anions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)