Diastereomeric hexacoordinate silicon complexes: preparation, structure and epimerization

Abstract

Abstract The synthesis of a neutral hexacoordinate silicon complex ( 6 ) with a chiral silicon and an adjacent chiral carbon center, via an intramolecular nucleophilic displacement, is described. 6 exists in a mixture of two diastereomers. One of the diastereomers has been characterized by an X-ray crystallographic analysis, and is found to have a nearly octahedral geometry about the silicon. 6 undergoes two intramolecular ligand-site exchhange processes, observable by NMR spectroscopy: reversible dissociation of the N–Si dative bond, leading to interchange of the N -methyl groups ( Δ G ∗ =16.7±0.2 kcal mol −1 at 365 K), and inversion of configuration at the silicon center, measured by selective inversion recovery NMR spectroscopy (21.0 kcal mol −1 at 350 K).