We have demonstrated that chiral silatranes can be prepared from terpene epoxides in very few steps, and have analysed the electron density distribution by the Bader technique. The weak Si-N bond is mainly ionic (bond order 0.270) and responsible for the enhanced hydrolytic stability compared with most other derivatives of silicic acid. Silicon ends up with a positive (3.34588) and nitrogen with a negative charge (-1.47333), which is somewhat counter-intuitive (the Si-N bond is normally formulated as a dative bond involving the nitrogen lone pair). The results show that the topological analysis of the electron density is possible even for such quite large systems. Calculations of the hyperpolarizability (for the non-linear optical properties) should therefore be feasible as well.

1998-06-18