Infrared and Raman Spectroscopic Studies of Tris(trimethylsilyl)silane Derivatives of (CH₃)₃Si)₃Si-X [X = H, Cl, OH, CH₃, OCH₃, Si(CH₃)₃]

IR and Raman spectra were measured to elucidate the vibrational structures of tris(trimethylsilyl)silane derivatives [((CH₃)₃Si)₃Si-X, X = H, Cl, OH, CH₃, OCH₃, and Si(CH₃)₃] in the fundamental state. Hartree-Fock (HF) and density-functional theory (DFT) calculations were carried out to study the molecular structure and the vibrational spectra. In the IR spectra, two scaling factors of 0.978 and 0.917 were applied to the low (below 2300 ㎝⁻¹) and the high (above 2300 ㎝⁻¹) energy fundamental frequencies giving rms deviations of 44.0 and 20.4 ㎝⁻¹, respectively. In the Raman spectra, however, a uniform scaling factor of 0.900 was applied to the whole spectra, yielding a rms deviation 40.0 ㎝⁻¹. Comparison between the experimental and the simulated IR and Raman spectra of the tris(trimethylsilyl)silane derivatives were made. We clearly observe the Si-H stretching fundamental at 2052 and 2048 ㎝⁻¹ in the IR and the Raman spectra, respectively. The intensities for the vibrations are relatively intense compared with those of the C-H stretching fundamental. The skeletal vibrations involving Si-Si are found to have relatively weak intensities in the IR and the Raman spectra. Pure Si-O stretching at 611 ㎝⁻¹ in the IR spectrum is clearly observed to have an intense absorption both in the IR and the Raman spectra. The strong IR intensity is due to the electronegativity difference between the corresponding two atoms.