[BMIm]₄[Sn₉Se₂₀]: Ionothermal Synthesis of a Selenidostannate with a 3D Open-Framework Structure

The reaction of [K4(H2O)4][SnSe4] with [BMIm][BF4] at 130–180 °C afforded [BMIm]4[Sn9Se20] (1). The anion of the title compound represents a unique three-dimensional (3D) open framework, based on a variety of interconnectivity modes of Sn/Se units that lead to a system of six intersecting channels. 1 comprises the first example of a binary 3D open-framework selenidostannate anion and the first 3D open-framework chalcogenido metalate to be conveniently obtained by ionothermal synthesis.