Vibrational study of eight‐membered titanium and germanium‐containing siloxane rings

By a condensation reaction of ^tBu₂Si(OH)₂(L) with titanium and germanium tetrahalides several eight‐membered titanium and germanium cyclosiloxane compounds were prepared in polar solvents. These were crystallized and identified by the usual physical techniques (¹H, ¹³C and ²⁹Si NMR spectroscopy, x‐ray diffraction and mass spectrometry). Raman and IR spectra were also recorded, which confirmed the structure obtained by x‐ray diffraction. The rings are well characterized by breathing modes which appear around 620–660 cm⁻¹ and Si‐O‐M stretching‐bending modes which appear around 950–1000 cm⁻¹. The vibrational modes characterizing the tert‐ butyl group are weakly coupled with those of the heterocycles. The corresponding observed bands are close to those observed for (L).