Vibrational frequencies of (CH3)3GeCCH and (CD3)3GeCCD and force field of trimethylgermylacetylene

Abstract The polarized Raman (50–3400 cm −1 ) spectra of (CH 3 ) 3 GeCCH and (CD 3 ) 3 GeCCD in the liquid phase and the i.r. (32–4000 cm −1 ) spectra of these compounds in the liquid and gas phases were obtained. All the active fundamentals except an internal torsion were assigned based on a molecular model of point group C 3ν . Each methyl group is expected to exist in a staggered arrangement with respect to the GeC bond and the neighbouring GeC bonds. General valence force constants of trimethylgermylacetylene were calculated by the least squares method. The calculated and observed frequencies agree to better than 6 cm −1 or 0.5 % for both the light and heavy compounds. The results are compared to corresponding quantities in some similar molecules.