Synthesis, characterization and structural aspects of 3-azidopropylsilatrane

Reaction of 3-chloropropyltriethoxysilane (1) with sodium azide (2) in the presence of phase transfer catalyst, tert-butylammonium bromide provided 3-azidopropyltriethoxysilane (3). This undergoes transesterification reaction with triethanolamine in the presence of KOH to form a new silatrane 3-azidopropylsilatrane (4). Multinuclear NMR (1H, 13C and 29Si), IR and elemental analyses support the structure of novel silatrane 4. 29Si NMR indicates the presence of penta-coordinated silicon atom, which is supported by X-ray studies. It revealed that Si is present in distorted trigonal bipyramidal environment with three O atoms in equatorial positions and N atom at one of the apical positions. The second axial position is occupied by long alkyl chain bearing azide moiety. The interaction of Si with N forms a transannular bond having 2.176 Å bond length.