Molecular, structure of (BuCl2SiSiCl2But)-Cl-t in the gas phase by electron diffraction and ab initio calculations. Molecular structures of the compounds (BuX2SiSiX2But)-X-t (X = Cl, Br or I) by vibrational spectroscopy, X-ray crystallography and ab initio calculations

The series of compoundsBu(t)X(2)SiSiX(2)Bu(t)(X = Cl, Br and I) have been s tudied by X-ray crystallography, vibrational spectroscopy and ab initio cal culations. The solids were all found to be anti and the vibrational spectra are consistent with this observation. The molecular structure of 1,2-di-te rt-butyltetrachlorodisilane (BuCl2SiSiCl2But)-Cl-t,has also been determined in the gas phase by electron diffraction (GED) and ab initio molecular-orb ital calculations. The conformation is distorted slightly from the fully st aggered arrangement, with phi (CSiSiC) 167.7(11)degrees. Important structur al parameters (r(a)) include: Si-Si 238.0(7) pm, Si-C 187.2(7) pm, C-C 154. 3(2) pm, C-H 114.2(4) pm, Si-Si-C 119.8(6)degrees, Cl-Si-Cl 105,5(8)degrees and C-Si-Si-C, 167.7(11)degrees. These experimental observations are suppo rted by theoretical predictions obtained at the MP2/6-31G* level.