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

By a condensation reaction of (t)Bu(2)Si(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 (H-1, C-13 and Si-29 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).