Reactions of niobium and tantalum hexanuclear halide clusters with cadmium(II) halides, diamagnetic and paramagnetic clusters with semiconducting properties

The diamagnetic [Ta6Cl12(H2O)(6)] [CdCl2X2]. 12H(2)O (X = Br, I) 1, 2 and [ M6Br12(H2O)(6)]-[CdBr2X2] . 12H(2)O (M = Nb, Ta; X = Cl, Br, I) 3-8 cluster s as well as paramagnetic [(Ta6Cl12)Cl(H2O)(5)] [CdBr4]. 6H(2)O 9 have been isolated. The crystal structures have been determined for [Nb6Br12(H2O)(6) ][CdBr4]. 12H(2)O 4, [Ta6Br12(H2O)(6)][CdBr4]. 12H(2)O 7 and [(Ta6Cl12)-Cl( H2O)(5)][CdBr4]. 6H(2)O 9. Octahedral cluster cations [M6Br12(H2O)(6)](2+) in 4, 7 and [(Ta6Cl12)-Cl(H2O)(5)](2+) in 9, together with [CdBr4](2-) anio n as discrete units are main structural building blocks. The crystal packin g of the cations and anions in a three-dimensional network in 4 and 7 is re alized via hydrogen bonds involving crystal and coordinated water molecules and Br- atoms from [CdBr4](2-) anions. The paramagnetic cluster 9 displays the quazionedimensional magnetic properties with intrachain antiferromagne tic interaction J = 68 K and the interchain interaction J' = 21 K. All comp ounds show semiconducting properties. The respective activation energies, E -al = 0.23 eV and E-a2 = 0.19 eV (the same values for 7 and 9) have been fo und. (C) 2001 Elsevier Science Ltd. All rights reserved.