D. Hnyk et al., AN ELECTRON-DIFFRACTION, AB-INITIO AND VIBRATIONAL SPECTROSCOPIC STUDY OF 1,2-DI-TERT-BUTYLDISILANE, Journal of molecular structure, 346, 1995, pp. 215-229
The molecular structure of 1,2-di-tert-butyldisilane has been accurate
ly determined by gas-phase electron diffraction (GED) and ab initio ca
lculations. These techniques show that the large majority of molecules
at room temperature have the anti conformation with overall symmetry
C-2, and vibrational spectra confirm this conclusion, Infrared spectra
of the gas and liquid phases, and Raman spectra of the liquid and sol
id phases, have been recorded for (CH3)(3)CSiH2SiH2C(CH3)(3) and (CH3)
(3)CSiD2SiD2C(CH3)(3). The most striking feature of this structure (r(
a)) is a relatively large deviation of the SiSiC angle from the parent
tetrahedral angle 109.5 degrees (113.7(3)degrees, GED; 114.4 degrees,
SCF/6-31G as calculated for the anti form). That the Si-Si bond leng
th does not show any substantial deviation from its usual value (234.8
(3) pm, GED; 236.8 pm, SCF/6-31G computed for the anti form) is also
substantiated by the value of the SiSi valence force constant (169 N m
(-1)) given by normal coordinate analysis. The t-butyl groups are tilt
ed so that the SI-C bonds (GED (SCF/6-31G): 190.1(1) (191.9)pm) do no
t coincide with the local C-3 axes of the C(CH3)(3) groups in which th
e C-C bond length is 154.1(1) (GED); 154.0 (SCF/6-31G) pm. The confor
mations along all the single bonds are more or less staggered.