A Quantum Mechanical Investigation of the Nature of the Dative Bond in Crystalline 1-Chlorosilatrane

The molecular geometry of crystalline 1-chlorosilatrane is computed at the self-consistent field (SCF) and density functional theory (DFT) levels of theory with the 6-31G* basis set and compared with experiment. The calculations reproduce the shortening of the Si-N distance in the crystal relative to the gas phase, in agreement with existing experimental data for methyl- and fluorosilatrane. The bond shortening is shown to be the result of a combination of a conformational change in the molecule and dipole-dipole interactions with the surrounding molecules in the crystal. The importance of the need to include long-range interactions in the calculation is demonstrated. The calculated electron density of chlorosilatrane is analyzed in terms of the natural bond orbital formalism (NBO), natural resonance theory (NRT), and the theory of atoms in molecules (AIM).