Noble Gas-Silicon Cations: Theoretical Insights into the Nature of the Bond

The structure, stability, and bonding situation of some exemplary noble gas-silicon cations were investigated at the MP2/aVTZ level of theory. The explored species include the mono-coordinated NgSiX(3)(+) (Ng = He-Rn; X = H, F, Cl) and NgSiF(2)(2+) (Ng = He-Rn), the di-coordinated Ar2SiX3+ (X = H, F, Cl), and the inserted FNgSiF(2)(+) (Ng = Kr, Xe, Rn). The bonding analysis was accomplished by the method that we recently proposed to assay the bonding situation of noblegas compounds. The Ng-Si bonds are generally tight and feature a partial contribution of covalency. In the NgSiX(3)(+), the degree of the Ng-Si interaction mirrors the trends of two factors, namely the polarizability of Ng that increases when going from Ng = He to Ng = Rn, and the Lewis acidity of SiX3+ that decreases in the order SiF3+ > SiH3+ > SiCl3+. For the HeSiX3+, it was also possible to catch peculiar effects referable to the small size of He. When going from the NgSiF(3)(+) to the NgSiF(2)(2+), the increased charge on Si promotes an appreciable increase inthe Ng-Si interaction, which becomes truly covalent for the heaviest Ng. The strength of the bond also increases when going from the NgSiF(3)(+) to the inserted FNgSiF(2)(+), likely due to the cooperative effect of the adjacent F atom. On the other hand, the ligation of a second Ar atom to ArSiX3+ (X = H, F, Cl), as to form Ar-2(SiX3+), produces a weakening of the bond. Our obtained data were compared with previous findings already available in the literature.

Automated summary

In this study, the structure, stability, and bonding situation of noble gas-silicon cations were investigated using theoretical calculations. The results show that the Ng-Si bonds are generally tight and have a partial covalent character. The degree of Ng-Si interaction in NgSiX(3)(+) is influenced by the polarizability of Ng and the Lewis acidity of SiX3+. Peculiar effects related to the small size of He were observed in HeSiX3+. The Ng-Si interaction in NgSiF(2)(2+) increases with the increased charge on Si, and the bond strength also increases in the inserted FNgSiF(2)(+) due to the cooperative effect of the adjacent F atom. On the other hand, the ligation of a second Ar atom to ArSiX3+ weakens the bond.