Organic Synthesis via Hypervalent, Hypercoordinate Molecules

This review describes synthetic applications of “hypervalent”, “hypercoordinate” molecules of the Group 14 Group 17 elements, in which there is an expansion of the valence octet of the central atom. Reactions of penta- and hexa-coordinate silicon compounds are categorized into five types, and examples are presented to demonstrate (1) the activation of Si-C, Si-H, and Si-O bonds towards electrophiles, (2) the template effect through inclusion of an electrophilic center into the coordination sphere, and (3) some contrasting stereochemical outcomes. The following representative examples are also described : (4) stereocontrol via hypercoordinate Sn (IV) and Sn (II) species, (5) ligand coupling in triaryl derivatives of P (V) and S (VI), and (6) phenyl-Bi (V) and allyl-I (III) compounds as phenyl and allyl cation equivalents, respectively.