Coinage-Metal Tellurides: Synthesis and Structural Characterization of the [(Te₄)M(μ-Te₄)M(Te4)]⁴⁻ Anions (M = Cu, Ag)

Reaction of Cu⁺ and Ag⁺ cations in DMF with a polytelluride solution in the presence of PEt₃, followed by addition of NEt₄Cl, affords the two new metal telluride salts [NEt₄]₄[(Te₄)M(μ-Te₄)M(Te₄)] (M = Cu, Ag), the first examples of soluble copper and silver tellurides. Single crystal X-ray diffraction results are as follows: Cu complex, space group P2₁/c, monoclinic, a = 10.564(2) Å, b = 10.697(2) Å, c = 25.740(5) Å, β = 94.55(3)°, Z = 2, R = 0.065 for 1701 independent observed reflections; Ag complex, space group P2₁/c, monoclinic, a = 10.584(2) Å, b = 10.763(2) Å, c = 25.895(5) Å, β = 94.01(3)°, Z = 2, R = 0.058 for 7232 independent observed reflections. The isostructural anions have crystallographically imposed centers of symmetry. In each anion, the metal atoms are bridged by a Te₄ chain and coordinated in a bidentate fashion by Te₄ rings. These anions have no known sulfur or selenium analogues.