Conformational analysis of some substituted silatranyl-carboxylic acids produced by computational study and NMR spectroscopy

Abstract

The structures of four silatrane compounds, silatranyl-carboxylic acid and its derivatives ( I, II, III, IV), are studied with molecular mechanics and NMR methods. The geometrical conformations of the molecules are calculated using full geometry optimization methods with MM2 and CNDO 2 . The conformations obtained are in agreement with results in the literature and with our X-ray and NMR experiments. However, there are some differences between the solid state, gas phase, and solution structures. The influence of the substituents (−COOH, −CH 3, −CHCH 2, −CH 3) is discussed. It has been found that substitution by the carboxyl group in the silatrane framework plays a more important role in influencing the transannular structure than does substitution in the equatorial position. The calculated and experimental results are presented and discussed in detail.