SPECTRA AND STRUCTURE OF SILICON CONTAINING COMPOUNDS .11. INFRARED AND RAMAN-SPECTRA OF 1,1-DIMETHYL-1-SILACYCLOBUTANE

The infrared spectra of 1,1-dimethyl-1-silacyclobutane in the vapor and solid phases have been recorded from 3300 to 80 cm-1. The Raman spectra of all three phases have been measured and depolarization data have been obtained for the gaseous and liquid states. An assignment of the fundamental vibrations is presented. The methyl torsional frequencies have been assigned to two weak bands appearing in the Raman spectrum of the gas phase at 177 and 172 cm-1. These values result in a barrier to internal rotation of 2.1 kcal mole-1. Evidence is presented for the existence of a quasi-planar conformer in the ambient temperature fluid phases, which obeys Cs selection rules in the low temperature solid state. This structure is compared to those of other silacyclobutanes and possible explanations given for the differences. © 1979.