The study of detection for transient silicon compuneds using a Fourier transform microwave spectrometer

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In order to investigate shote lived dimethylsilane which plays important role in organosilicon reactions, we tried to detect dimethylsilane in the pyrolysis and discharge reactions of dimethylchlorosilane and trimethylenedimethylsilane. It has not been observed by means of a Fourier transform microwave spectrometer, however, many rotational transitions of the parent species were observed. Therefore the molecular structures and vibrational motions of DMC1Si and TMDMSi were studied. In the addition, the 101-000 transition of a short lived molecule, Si2H2, was detected during a discharge reaction of silane.The microwave spectra of five isotopic species of chlorodimethylsilane have been investigated in the region 5 to 20 GHz using a Fourier transform microwave spectrometer. The molecular structure of (CH_3)_2SiHCl obtained by the substitution method is the following one: r_s(Si-Cl) = 2.0604 (10) A^^°, r_s (Si-C) = 1.8542 (10) A^^°, /ClSiC = 108.43 (20)°, and /CSiC = 112.32 (15)°. The quadrupole coupling constants of the chlorine atom was obtained and yielded x_<zz> = -35.556 (6) MHz and 65 % as an ionic character of the chlorine atom. The estimated value of the potential barrier V_3 of internal rotation of two methyl tops is in agreement with those of the related molecules.The a-type transitions of isotopic species, normal, ^<29>Si, ^<30>Si, and ^<13>C, of 1, 1-dimethylsilacyclobutane were observed and assigned. Each transition except ^<13>C species in the methyl group has six components because of the splittings due to the internal rotation of two methyl tops and the ring puckering. The observed spectra of two ^<13>C species in the methyl group were much complicated and distinguished from the spectra of two ^<13>C species in the ring. The estimated value of the potential barrier V_3 of internal rotation of two methyl tops is in agreement with those of the related molecules.