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 polar environment that could produce an electron deficiency on the hydrogen atom. In addition, analogous derivatives where the silicon atom has been replaced by a carbon atom have been considered. In all cases, ammonia has been 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 been 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 theoretical study on these HB complexes between ammonia and the silicon derivatives provides long HB distances (2.4 to 3.2 Å) and small interaction energies (−2.4 to −0.2 kcal/mol). In all cases, the HBs of the corresponding carbon analogs show shorter interaction distances corresponding to stronger complexes. The CSD search provides a small number of short interactions between Si and other heavy atoms in agreement with the small stabilizing energy of the Si–HN HB and the lack of SiH bond in polar environment within the database.