Abstract: | The reaction of W6Br12 with CuBr sealed in an evacuated silica tube at the temperature gradient 925/915 K and annealing at 625/300 K yields a mixture of orthorhombic α-Cu2[W6Br14] and cubic β-Cu2[W6Br14] in the low temperature zone. α-Cu2[W6Br14] crystallizes in the space group Pbca (no. 61), a = 15.126 Å, b = 9.887 Å, c = 15.954 Å, Z = 4, oP88, and β-Cu2[W6Br14] crystallizes in the space group Pn3 (no. 201), a = 13.391 Å, Z = 4, cP88. The crystal structures are built up by [(W6Br)Br]2– cluster anions and Cu+ cations. The cluster anions show only in the peripheral shells small deviation from m3m symmetry (d(W–W) = 2.630 Å; d(W–Bri) = 2.618 Å; d(W–Bra) = 2.614 Å). The anions are arranged in a slightly compressed bcc pattern (α) and ccp (β) pattern, respectively. The Cu+ cations are trigonal-planar coordinated by Bra ligands with d(Cu–Br) = 2.377 Å (α) and 2.378 Å (β). The cubic β-modification is diamagnetic with an unexpected large susceptibility (χmol = –884 × 10–6 cm3 mol–1) and have a band gap of 2.8 eV. It decomposes under dynamic vacuum in two steps at 795 K und 1040 K. |