The Intriguing Structural Characteristics of the Heterosiloxane Molecule Na₄[Sb₂O(OSiMe₃)₈]

Treatment of Sb(OSiMe₃)₃ with NaOSiMe₃ in the molar ratio 1:2 in hexane at ambient temperature leads to the formation of Me₃SiOSiMe₃ and a crystalline complex of the formula Na₄[Sb₂O(OSiMe₃)₈] in ca. 35% yield. The composition of the product has been confirmed by elemental analysis and negative‐ion CI mass spectrometry. The single crystal X‐ray structure analysis (rhombohedral, space group R\documentclass{article}\pagestyle{empty}\begin{document}$\bar{3}$\end{document}c, Z6) resulted in a disorder model for the complex with pseudo‐cubic symmetry owing to virtually random distribution of sodium and antimony atoms over the vertices of an oxygen‐centered octahedron with the eight silyloxy groups capping the faces. Low solubility in non‐coordinating solvents prevented solution NMR studies, but solid‐state NMR investigations using cross polarization and magic‐angle spinning techniques (¹³C, ²⁹Si) allowed the assignment of a point group C_2v structure with the Sb^III atoms in cis position relative to the oxo center of the complex.