CONFORMATIONAL-ANALYSIS OF SOME SUBSTITUTED SILATRANYL-CARBOXYLIC ACIDS PRODUCED BY COMPUTATIONAL STUDY AND NMR-SPECTROSCOPY

The structures of four silatrane compounds, silatranyl-carboxylic acid and its derivatives (I, II, III, IV), are studied with molecular mech anics and NMR methods. The geometrical conformations of the molecules are calculated using full geometry optimization methods with MM2 and C NDO/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 str uctures. The influence of the substituents (-COOH, -CH3, -CH=CH2, -CH3 ) is discussed. It has been found that substitution by the carboxyl gr oup in the silatrane framework plays a more important role in influenc ing the transannular structure than does substitution in the equatoria l position. The calculated and experimental results are presented and discussed in detail.