Molecular structure and conformations of 2,2-di-tert-butyl-1,3-diaza-2-silacyclopentane: gas electron diffraction and quantum chemical calculations

Heinz Oberhammer; Georgiy V Girichev; Nina I Giricheva; Alexander V Krasnov; Uwe Klingebiel

doi:10.1021/ic0497836

Molecular structure and conformations of 2,2-di-tert-butyl-1,3-diaza-2-silacyclopentane: gas electron diffraction and quantum chemical calculations

Inorg Chem. 2004 May 31;43(11):3537-42. doi: 10.1021/ic0497836.

Authors

Heinz Oberhammer¹, Georgiy V Girichev, Nina I Giricheva, Alexander V Krasnov, Uwe Klingebiel

Affiliation

¹ Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany. heinz.oberhammer@uni-tuebingen.de

PMID: 15154819
DOI: 10.1021/ic0497836

Abstract

The geometric structure and conformational properties of the saturated five-membered-ring compound 2,2-di-tert-butyl-1,3-diaza-2-silacyclopentane, (t-Bu)(2)Si(NH)(2)(CH(2))(2), was investigated by gas electron diffraction and quantum chemical methods (B3LYP and MP2 with 6-31G basis sets). The compound exists as a mixture of two conformers, both possessing a twist conformation and C(2) symmetry. In the prevailing form (76(6) % at 305 K) the N-H bonds stagger the adjacent CH(2) groups, and in the minor form the N-H bonds eclipse the CH(2) groups. This conformational mixture corresponds to a free energy difference of DeltaG degrees = 0.69(19) kcal/mol. The B3LYP method predicts a preference for the eclipsed conformer. The largest torsion occurs around the C-C bond with tau(NCCN) = 29.2(24) degrees. The degree of puckering in the title compound is considerably smaller than that in silacyclopentane with tau(CCCC) = 49.7(14) degrees. This has been rationalized by larger angle strain in the title compound.