NMR and Quantum-Chemical Studies of Electrostatically Stabilized 1-(N,N-Substituted-aminiomethyl)spirobi [3-oxo(2,5-dioxa-1-silacyclopentan)]ates (ES-Silanates)

Abstract

1-(N,N-substituted-aminiomethyl)spirobi[3-oxo(2,5-dioxa-1-silacyclopentan)]ates were investigated using NMR, X-ray, and quantum-chemical methods. The free activation parameters for the inversion of “ammonium-amine nitrogen” and the chirality change at the pentacoordinated silicon were determined by dynamic NMR spectroscopy. The latter proceeds via the dissociation of Si[BOND]O bonds. The results were confirmed by quantum-chemical calculations, the experimental observation of cross-peaks in 2D-EXSY NMR spectra, and the spirocycle exchange reactions. Transition pathways between the different diastereomers in solution were analyzed