Matrix Isolation Laser Raman Spectroscopy. I. Vibrational Raman Spectra and Depolarization Measurements for Matrix Isolated Group IVa Dihalides, MX2 and MXY (where M = Ge, Sn, Pb and X, Y = Cl, Br), in Solid Argon and Nitrogen

Abstract

The vibrational Raman spectra together with polarization data are reported for most of the monomeric dihalides MX2 and mixed dihalides MXY of Group IVa (where M = Ge, Sn, or Pb and X, Y = Cl or Br) isolated in both argon and nitrogen matrices at 4.2°K. Laser induced resonance fluorescence effects which interfere with gas phase Raman studies are eliminated in Raman studies of matrix isolated dihalides. The isotope components of ν1 and ν3 are clearly resolved in the case of PbCl2 in argon and assigned to Pb35Cl2, Pb35Cl37Cl, and Pb37Cl2. Diffusion controlled warmup data are recorded for all species in the temperature range 4.2–40°K. All isolated monomers were found to diffuse rapidly at 30–35°K and only in the case of GeCl2 was a definite, stepwise polymerization process observed. The final spectrum obtained by warming GeCl2 showed the presence of a polymeric structure containing both terminal and bridging chlorine atoms. The matrix Raman results demonstrate that spectral sensitivities and resolution can be achieved which are comparable with the complimentary matrix infrared data and that matrix Raman polarization measurements add a valuable new tool for matrix isolation studies.