Infrared and Raman spectra of 1,1-dibromodisilanes and STO-3G∗ calculations

Infrared and Raman spectra in the gas phase are reported for 1,1-Si2H4Br2 and 1,1-Si2D4Br2. With the help of STO-3G* calculations for these species and for Si2H5Br and Si2D5Br, nearly all the fundamentals of the dibromo compounds are assigned and reliable estimates made for the remainder, except the silyl torsions. Minimal basis set calculations of vibration frequency are useful if suitable scaling is applied, based on analogous compounds. Using substituent effects, harmonic local mode calculations and several impurity bands in the 1,1-dibromodisilane species, SiH stretching frequencies are predicted for tri-, tetra- and penta-bromodisilanes as well as for 1,2-dibromodisilane conformers.