RAMAN AND INFRARED VIBRATIONAL-SPECTRA, NORMAL-COORDINATE ANALYSIS AND AB-INITIO CALCULATIONS OF 1,1,2,2-TETRACHLORODISILANE AND AB-INITIO CALCULATIONS OF HEXACHLORODISILANE

The infrared and Raman vibrational spectra of 1,1,2,2-tetrachlorodisil ane (Cl2HSiSiHCl2) and its d(2)-isotopomer Cl2DSiSiDCl2 were measured and assigned with the aid of normal coordinate analyses and also ab in itio RHF geometry optimizations and harmonic wavenumber calculations u sing the GAMESS quantum chemistry software. The calculations were perf ormed employing pseudopotentials for the core electrons of the heavy a toms and a valence double zeta basis with polarization functions on al l atoms, The spectra clearly prove the simultaneous existence of the g auche and the anti conformer in the gas and the liquid phase, The ener gy difference between the conformers is 1.9 +/- 0.7 kJ mol(-1), as ded uced from temperature-dependent Fourier transform Raman spectra, with the gauche conformer being more stable, Ab initio RHF calculations of the harmonic force field and geometry and harmonic wavenumbers at the same level of theory were also performed for hexachlorodisilane (Si2Cl 6), (C) 1997 John Wiley & Sons, Ltd.