The formation of H···X hydrogen bond, C···X carbon-halide or Si···X tetrel bonds on the silylene-halogen dimers (X = F or Cl): intermolecular strength, molecular orbital interactions and prediction of covalency

The optimized geometries of the CH4Si···F2, C2H6Si···F2, CH4Si···Cl2 and C2H6Si···Cl2 complexes were obtained at the MP2/aug-cc-pVDZ level of theory. By means of the results of structure, vibration modes, molecular topology, bonding energy, thermodynamic stability and molecular orbital analysis, the interaction strength was examined by taking into account the presence of the σ-hole effect manifested on the halogen molecules. The topography of the quantum theory of atoms in molecules, the charge transfer determined by means of the natural bond orbitals as well as by the electrostatic potentials using a grid-based method and the graphical visualizer of non-covalent interaction were used to unveil if these systems are dominated by hydrogen bond, carbon-halide bond or tetrel bond. At last, the intermolecular covalency was analyzed through the symmetry-adapted perturbation theory at light of the EInd(R) /EElst(1) ratio and interaction distance.