Molecular complexes between silicon derivatives and electron-rich groups

Theoretical calculations on a series of SiXY3. . . ZW complexes, where X and Y are H, F, and Cl, and Z corresponds to an electron donor atom (ZW = NH3, NCH, CNH, OH2, FH), were performed. The calculations were carried out using B3LYP/6-311++G**, MP2/6-311++G** and MP2/6-311++G(2d,2p) computational methods. The electron density was characterized by means of the atoms in molecules (AIM) methodology, and the interaction nature was studied with the NBO method. Finally, the effect of the complexation on the nuclear chemical shieldings was evaluated with the GIAO method. The results display a wide range of interaction distances that vary from 2.1 to 4.1 Angstrom. The complexes with shorter interaction distances (similar to2.1 Angstrom) show important distortion effects and large dipole moment enhancements. The NBO analysis indicates that in those complexes an ionic interaction is formed between the Si and Z atoms. Comparison of the chemical shieldings of the complexes and the monomers indicates that these interactions could be detected experimentally using Si-29 NMR. In addition, in the case of the complexes with NH3 and OH2, the use of N-15 NMR and O-17 NMR could be adequate to check the potential formation of the corresponding complexes.