Trimethylsilyl derivatives for the study of silicate structures. Part 5. Trimethylsilylation of dioptase

Abstract

The technique of trimethylsilylation developed earlier has been applied to the mineral dioptase Cu₆Si₆O₁₈·6H₂O. The main products are shown to be Si₆O₁₈(SiMe₃)₁₂ and Si₆O₁₇(SiMe₃)₁₀ by gas-liquid chromatography and mass spectrometry. Three isomers of Si₆O₁₈(SiMe₃)₁₂ and three isomers of Si₆O₁₇(SiMe₃)₁₀ are observed in the products, depending on the conditions of trimethylsilylation and the type of chromatographic column employed. When HCl is added to the reaction mixture the predominant product is Si₆O₁₇(SiMe₃)₁₀ indicating that the ion [Si₆O₁₈]^12– is converted mainly into [Si₆O₁₇]^10– in an acidic aqueous medium.