On the Synthesis and Reactivity of Highly Labile Pseudohalogen Phosphenium Ions

The synthesis and characterization of salts bearing highly labile pseudohalogen-substituted aminophosphenium cations of the type [(Me3Si)2NPX]­[GaCl4] (X = NCO, NCS, O­(SiMe3)) and their respective reactivity toward Lewis bases (4-dimethylaminopyridine, dmap) and dienes (2,3-dimethyl-1,3-butadiene, dmb; 1,3-cyclo-hexadiene, chd) are described. As π-acidic species, aminophosphenium cations react with dmap at low temperatures to yield adduct salts of the type [(Me3Si)2NP­(dmap)­X]­[GaCl4] (X = Cl, N3, NCO) which were fully characterized. In the reaction with dienes at −50 °C, salts bearing phospholenium cations were obtained that could be structurally characterized. The crystal structures of novel 7-phosphanorbornenium cations of the type [(Me3Si)2NP­(C6H8)­X]­[GaCl4] (X = Cl, N3, NCO) are reported. All compounds were further investigated by means of density functional theory, and the bonding situation was accessed by Natural Bond Orbital (NBO) analysis.