Crystal structures determined for several neutral hexacoordinate bis(N-->Si) chelates revealed in all cases near octahedral geometries with the nitrogen ligands in relative trans and the monodentate Ligands in cis positions. To assign the two consecutive intramolecular ligand-site exchange processes (reported earlier), a bis-chelate was prepared containing a chiral carbon center in each of the chelate rings (14). By means of a phase sensitive NOESY NMR spectrum it was possible to conclude that the lower-barrier process involved exchange of diastereotopic groups only within each diastereomer, and not between them, resulting in the assignment of this process to the direct nondissociative interchange of the monodentate ligands (X, Y). The Si-Cl bond lengths were found to inversely correlate with the lower of the activation barriers. Dissociation-recombination of-the N-->Si dative bond was also observed by the high-temperature NMR spectra. Lack of correlation between Si-N distances in the crystals and activation barriers led to the conclusion that Si-N dissociation was not involved in the measured rate processes, but followed, at slightly higher temperature, the epimerization at the silicon center by exchange of the two oxygen sites.