Electrochemical Synthesis of [NEt₄]₂[enH]₂[Ge₂Se₆] and [NEt₄]₄[Sn₄Se₁₀]

Abstract

[NEt4]2[enH]2[Ge2Se6] and [NEt4]4[Sn4Se10] have been synthesized electrochemically by the reduction of metal chalcogen alloys in an electrolyte solution of NEt4Br in ethylenediamine. The structures of both compounds have been determined by single-crystal X-ray methods. [NEt4]2[enH]2[Ge2Se6] crystallizes in the triclinic space group Ci1−P1̄ with one formula unit in a cell of dimensions a = 7.805(4) Å, b = 10.747(6) Å, c = 11.445(6) Å, α = 110.33(2)°, β = 97.19(3)°, γ = 92.62(2)°, and V = 889.0(8) Å3 (T = 115 K). Final agreement indices for [NEt4]2[enH]2[Ge2Se6] are 0.116 for Rw(Fo2) for all the 2982 data and 0.055 for R1 for the 1958 reflections with Fo2 ≥ 2σ(Fo2) (158 variables). [NEt4]4[Sn4Se10] crystallizes in the cubic space group −P4̄3n with eight formula units in a cell of dimensions a = 22.170(7) and V = 10897(6) Å3 (T = 115 K). Final agreement indices for [NEt4]4[Sn4Se10] are 0.123 for Rw(Fo2) for all the 1490 data and 0.057 for R1 for the 1138 data with Fo2 ≥ 2σ(Fo2) (90 variables). The [Ge2Se6]4- anion is composed of a pair of edge-sharing tetrahedra. Each of the two independent [Sn4Se10]4- anions has the adamantane-type structure consisting of four Sn tetrahedra, each of which shares three edges with three similar tetrahedra; the symmetry of one anion is 4̄ (S4) while that of the other is 23 (T). Although both the [Ge2Se6]4- and [Sn4Se10]4- anions are new, each has group 14 structural analogues.