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

Summary

The disproportionation reaction of a metastable Sn(I) chloride solution, obtained via the preparative co-condensation technique, is used for the synthesis of a metalloid tin cluster compound.

Abstract

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.

Introduction

Due to recent progress in the field of nanotechnology, the nanoscale size range between molecules and the solid state became more and more important and is the focus of various research efforts¹. Research with nanoscaled compounds is especially of interest for metals or semimetals, as drastic changes take place during the transformation from small molecular species (e.g., oxides, halides: non-conducting; e.g., AlCl₃, AuCl₃, GeO₂, etc.) to metalloid clusters² of the general formulae M_nR_m (n>m; M = metal such as Al, Au, Sn, etc.; R = ligand such as S....

Protocol

CAUTION! Please consult all relevant material safety data sheets (MSDS) before use. Several of the chemicals used in these syntheses are acutely toxic, pyrophoric, and carcinogenic. Nanomaterials may have additional hazards compared to their bulk counterpart. Please use all appropriate safety practices when performing a reaction, including the use of engineering controls (fume hood and glovebox) and personal protective equipment (safety glasses, gloves, lab coat, full length pants, and closed-toe shoes). Portions of the following procedures involve standard air-free Schlenk techniques. The co-condensation apparatus applied contains a 20 kW high-freque....

Results

The principle of the matrix isolation technique in conjugation with the preparative co-condensation technique is shown (Figure 1), as well as the setup of the co-condensation apparatus (Figure 2) and the graphite reactor (Figure 3). Figures 4 and 5 show photos of the assembly of the co-condensation apparatus. In Figure 6, the gas supply components with the mass flow controller are shown. .......

Discussion

By applying the preparative co-condensation technique (Figure 1)²⁵, novel materials based on molecules like SnBr are obtained. Due to the high flexibility in temperature, pressure, metal, and reactive gas, a large variety of metastable solutions of high reactive species can be synthesized. For example, subhalides of silicon and germanium are already obtained in this way. However, finding the right conditions to obtain a metastable solution for further synthesis is not trivial, and the solution.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Tin, 99.999%	ABCR	AB122397
Hydrogen chloride N28, 99.8%	Air Liquide	P0820S10R0A001	Toxic
Toluene anhydrous, 99.8%	Sigma Aldrich	244511
Tri-n-butylphosphine, >93.5%	Sigma Aldrich	90827	Toxic
TMEDA, >99.5%	Sigma Aldrich	411019
12-crown-4	Sigma Aldrich	194905	Toxic
THF anhydrous, >99.9%	Sigma Aldrich	401757
Sodium, 99.95%	Sigma Aldrich	262715
Benzophenone, >99%	Sigma Aldrich	427551
Differential pressure manometer	MKS	MKS Baratron 223B
Mass flow controller	Bronckhorst	Low Δp flow mass flow controller
High frequency generator	Trumpf Hüttinger	TruHeat MF 5020
NMR spectrometer	Bruker	Bruker DRX-250
Glovebox	GS Systemtechnik
Argon 5.0	Westfalen
Nitrogen 4.8	Westfalen
Graphite	SGL
Quartz glass tube	Gebr. Rettberg GmbH
Steel transferring cannula	Rohre Ketterer
Balance	Kern	Kern PFB200-3
Oil diffusion pump	Balzers	Balzers Diff900
Rotary vane pump	Balzers	Balzers QK100L4D
Pyrometer	Sensotherm	6285
Schlenk tubes with glassy stopcocks	Gebr. Rettberg GmbH	J.-Young-type valve with glassy stopcock