Raman and infrared vibrational spectra, ab initio calculations and normal coordinate analyses for 1,2-dimethyltetrachlorodisilane and 1,2-dimethyltetrachlorodisilane-d 6

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The Raman spectra of CH 3Cl 2SiSiCl 2CH 3 and CD 3Cl 2SiSiCl 2CD 3 between 3000 and 30 cm −1 have been recorded at various temperatures. The infrared spectra at ambient temperature were recorded from 3000 to 50 cm −1. Both isotopomers exist as a mixture of gauche and anti rotamers at room temperature. The energy difference E anti− E gauche was determined from the Raman spectra as being −0.9±0.2 kJ mol −1 for CH 3Cl 2SiSiCl 2CH 3 and −1.2±0.2 kJ mol −1 for CD 3Cl 2SiSiCl 2CD 3. Assisted by ab initio calculations, the vibrational spectra have been assigned using C 2h symmetry for the anti rotamers and C 2 symmetry for the gauche rotamers. Scaled and unscaled harmonic frequencies and harmonic symmetry force constants have been reported for both rotamers, and normal coordinate analyses have been carried out. Potential energy distributions have been reported.