Modified Tellurium Subhalides in the New Structure Type [Te15X4]n[MOX4]2n (M = Mo,W; X = Cl,Br)

The reactions of Te₂Br with MoOBr₃, TeCl₄ with MoNCl₂/MoOCl₃, and Te with WBr₅/WOBr₃ yield black, needle-like crystals of Te₁₅X₄]MOX₄]₂ (M = Mo, W; X = Cl, Br). The crystal structure determinations Te₁₅Br₄]MoOBr₄]₂: monoclinic, Z = 1, C2/m, a = 1595.9(4) pm, b = 403.6(1) pm, c = 1600.4(4) pm, β = 112.02(2)°; Te₁₅Cl₄]MoOCl₄]₂: C2/m, a = 1535.3(5) pm, b = 402.8(2) pm, c = 1569.6(5) pm, β = 112.02(2)°; Te₁₅Br₄]WOBr₄]₂: C2, a = 1592.4(4) pm, b = 397.5(1) pm, c = 1593.4(5) pm, β = 111.76(2)° show that all three compounds are isotypic and consist of one-dimensional (Te₁₅X₄]²⁺)_n and (MOX₄]^?)_n strands. The structures of the cationic strands are closely related to the tellurium subhalides Te₂X (X = Br, I). One of the two rows of halogen atoms that bridges the band of condensed Te₆ rings is stripped off, and additionally one Te position has only 75% occupancy which leads to the formula (Te₁₅X₄]²⁺)_n (X = Cl, Br) for the cation. The anionic substructures consist of tetrahalogenooxometalate ions MOX₄]^? that are linked by linear oxygen bridges to polymeric strands. The compounds are paramagnetic with one unpaired electron per metal atom indicating oxidation state M^v, and are weak semiconductors.