The Synthesis of [Sn₁₀(Si(SiMe₃)₃)₄]^2- Using a Metastable Sn(I) Halide Solution Synthesized via a Co-condensation Technique

The number of well-characterized metalloid tin clusters, synthesized by applying the disproportionation of a metastable Sn(I) halide in the presence of a sterically demanding ligand, has increased in recent years. The metastable Sn(I) halide is synthesized at "outer space conditions" via the preparative co-condensation technique. Thereby, the subhalide is synthesized in an oven at high temperatures, around 1,300 °C, and at reduced pressure by the reaction of elemental tin with hydrogen halide gas (e.g., HCl). The subhalide (e.g., SnCl) is trapped within a matrix of an inert solvent, like toluene at -196 °C. Heating the solid matrix to -78 °C gives a metastable solution of the subhalide. The metastable subhalide solution is highly reactive but can be stored at -78 °C for several weeks. On heating the solution to room temperature, a disproportionation reaction occurs, leading to elemental tin and the corresponding dihalide. By applying bulky ligands like Si(SiMe₃)₃, the intermediate metalloid cluster compounds can be trapped before complete disproportionation to elemental tin. Hence, the reaction of a metastable Sn(I)Cl solution with Li-Si(SiMe₃)₃ gives [Sn₁₀(Si(SiMe₃)₃)₄]^2- 1 as black crystals in high yield. 1 is formed via a complex reaction sequence including salt metathesis, disproportionation, and degradation of larger clusters. Further, 1 can be analyzed by various methods like NMR or single crystal X-ray structure analysis.