Neutral and cationic phosphoramide adducts of silicon tetrachloride: Synthesis and characterization of their solution and solid-state structures

The solution and solid-state structures of hexamethylphosphoramide (HMPA) adducts of tetrachlorosilane (SiCl4) are discussed. In solution, the meridional and facial isomers of the hexa-coordinate cationic complex 3HMPA center dot SiCl3+ Cl- (2) predominate at all HMPA concentrations, and are in equilibrium with the hexa-coordinate neutral trans- and cis-2HMPA center dot SiCl4 complexes (1), as well as the penta-coordinate cationic cis-2 HMPA center dot SiCl3+Cl- (3). Single crystal X-ray analyses are reported for the ionized mer-3HMPA center dot SiCl3+HCl2- and the neutral trans-2HMPA center dot SiCl4 complexes.