Clusterization Effect on the²⁹Si NMR Signal of a Spiro Silicon Atom

Abstract

Si14 cluster 3 containing a spiro silicon atom was obtained by the Wurtz-type coupling of 1,1,2,2-tetrachlorocyclopentasilane 1 with sodium. The structure and properties were studied by X-ray crystallography, spectroscopy, and theoretical calculations. The 29Si NMR signal of the spiro silicon atom was observed in the unusually downfield region at 104.2 ppm. The analysis of this result shows the clusterization effect on the 29Si NMR signal of the spiro silicon atom.

Isolable Spirocyclic Silylone: π-Delocalized Spiro[3.3]heptasila-2,6-diylidone

“…−100 ppm) in saturated spirooligosilanes. 26 The molecular structure of 2 obtained by X-ray crystallography (Figure 1b) shows that the two spirocyclic rings (Si1Si2Si3Si4, Si4Si5Si6Si7) are planar and linked by the spiro-Si4 atom. These two planes are perpendicular to each other, with a dihedral angle of 89.9°.…”

“…Additionally, the 29 Si NMR signal for Si4 (−8.5 ppm) is downfield-shifted in comparison with that of the spiro-silicon center ( ca . −100 ppm) in saturated spirooligosilanes …”