Theoretical study of the Si-H group as potential hydrogen bond donor

The ability of the Si-H group as hydrogen bond (HB) donor has been studied theoretically. Most of the selected molecules include the Si-H group in a p olar environment that could produce an electron deficiency on the hydrogen atom. In addition, analogous derivatives where the silicon atom has been re placed by a carbon atom have been considered. In all cases, ammonia has bee n used as HB acceptor. The calculations have been carried out at the MP2/6- 311++G** computational level. The electron density of the complexes has bee n characterized within the atoms in molecules (AIM) framework. A search in the Cambridge Structural Database (CSD) has been carried out to verify the existence of this kind of interactions in solid phase. The results of the t heoretical study on these HB complexes between ammonia and the silicon deri vatives provides long HB distances (2.4 to 3.2 Angstrom) and small interact ion energies (-2.4 to -0.2 kcal/mol). In all cases, the HBs of the correspo nding carbon analogs show shorter interaction distances corresponding to st ronger complexes. The CSD search provides a small number of short interacti ons between Si and other heavy atoms in agreement with the small stabilizin g energy of the Si-H...N HB and the lack of SiH bond in polar environment w ithin the database. (C) 2002 John Wiley & Sons, Inc.