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·SiCl₃⁺ Cl (2) predominate at all HMPA concentrations, and are in equilibrium with the hexa-coordinate neutral trans- and cis-2 HMPA·SiCl₄ complexes (1), as well as the penta-coordinate cationic cis-2 HMPA·SiCl₃⁺ Cl ^- (3). Single crystal X-ray analyses are reported for the ionized mer-3HMPA·SiCl₃⁺ HCl₂^- and the neutral trans-2 HMPA·SiCl₄ complexes.