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 (SiCl 4 ) are discussed. In solution, the meridional and facial isomers of the hexa‐coordinate cationic complex 3 HMPA ⋅ SiCl 3 +  Cl − ( 2 ) predominate at all HMPA concentrations, and are in equilibrium with the hexa‐coordinate neutral trans ‐ and cis ‐2 HMPA ⋅ SiCl 4 complexes ( 1 ), as well as the penta‐coordinate cationic cis ‐2 HMPA ⋅ SiCl 3 +  Cl − ( 3 ). Single crystal X‐ray analyses are reported for the ionized mer ‐3 HMPA ⋅ SiCl 3 +  HCl 2 − and the neutral trans ‐2 HMPA ⋅ SiCl 4 complexes.