THE STEREOCHEMISTRY OF NUCLEOPHILIC SUBSTITUTION AT TETRACOORDINATED SILICON

Abstract During the past decade experimental work, largely through the efforts of Corriu1.2a-c and co-workers, has greatly expanded the reaction chemistry of tetra-coordinated silicon compounds that had its initial basis arising from the pioneering work of Sommer 2d and co-workers. A large body of the results are interpretable in terms of reaction mechanisms involving pentacoordinated species. This has given rise to some proposed pathways for nucleophilic displacement that complement those in phosphorus chemistry 3 These are illustrated in Figure 1 for (a) an inversion process proceeding by way of nucleophilic attack at a tetrahedral face resulting in the formation of a transient trigonal bipyramid with the entering and leaving groups in apical positions and (b) a retention process governed again by facial attack by the nucleophile, only this time yielding a transient trigonal bipyramid with the leaving group in an adjacent equatorial position, as postulated in phosphorus chemistry,3.4 pseudorotation is e...