Zwitterionic Pentacoordinate Silicon Compounds

Abstract

Publisher Summary The chemistry of zwitterionic pentacoordinate silicon compounds is developed systematically. These compounds contain a silicate moiety with five covalent siliconelement bonds and an onium group. This chapter discusses a completely different class of pentacoordinate silicon compounds: zwitterionic λ 5 Si -silicates. These molecular compounds contain a pentacoordinate silicon atom and a tetracoordinate nitrogen atom. The syntheses, structures, and properties of compounds of zwitterionic λ 5 Si -silicates are discussed. The zwitterionic λ 5 Si -silicates are high-melting crystalline solids that are almost insoluble in nonpolar organic solvents and exhibit poor solubility in polar organic solvents. The crystals of these compounds consist of highly polar molecular building blocks that undergo intermolecular dipolar interactions. Different methods are used for their syntheses, some of these methods involving remarkable Si-C cleavage reactions. The products isolated directly from the reaction mixtures are well-crystallized solids, suitable for characterization by single-crystal X-ray diffraction and solid-state nuclear magnetic resonance (NMR) spectroscopy. The zwitterions are neutral molecules and are chiral, with a chiral λ 5 Si -silicates skeleton. Zwitterionic compounds are characterized by unique properties that arise from the charge separation in these molecules.