Vibrational spectra, theoretical calculations, and structure of 4-silaspiro(3,3)heptane

Theoretical computations have been carried out for 4-silaspiro(3,3)heptane (SSH) in order to calculate its structure and vibrational spectra. SSH was found to have two puckered four-membered rings with dihedral angles of 34.2 degrees and a tilt angle of 9.4 degrees between the two rings. The puckering and tilting reduce the D-2d symmetry to C-2. Nonetheless, the vibrational assignments can be done quite well on the basis of D-2d symmetry. This is confirmed by the fact that all but the lowest E vibrations show insignificant splitting into A and B modes of C-2 symmetry. However, the observed splittings of the lowest frequency modes do confirm the lower conformational symmetry. The calculated infrared and Raman spectra were compared to the experimental spectra collected for the vapor, liquid, and solid states, and the agreement is excellent. (C) 2014 Elsevier B.V. All rights reserved.