Conformational properties of the methylated disilanes MeX2SiSiX2Me (X = H, F, Br and I):: a combined ab initio and vibrational spectroscopic study

Together with ab initio calculations, Raman spectra of the methylated disilanes MeX2SiSiX2Me (X = H, F, Br and I) unambiguously prove the presence of two rotamers, anti and gauche in the liquid state. Energy differences between rotational isomers have been determined from variable temperature Raman spectra employing Van't Hoff plots of the logarithm of intensity ratios vs. the inverse temperature. For the disilanes with X = F, Br and I the anti conformation is preferred in the liquid state. For MeH2SiSiH2Me the gauche rotamer is slightly stabilized by 0.43 kJ mol(-1). Vibrational spectra have been assigned by the help of normal coordinate analyses using optimized geometries and ab initio symmetry force fields, (C) 1998 Elsevier Science B.V. All rights reserved.