The synthesis and characterization of salts bearing highly labile pseudohalogen-substituted aminophosphenium cations of the type [(Me3Si)(2)NPX][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 pi-acidic species, aminophosphenium cations react with dmap at low temperatures to yield adduct salts of the type [(Me3Si)(2)NP(dmap)X][GaCl4] (X = Cl, N-3, NCO) which were fully characterized. In the reaction with dienes at -50 degrees C, salts bearing phospholenium cations were obtained that could be structurally characterized The crystal structures of novel 7-phosphanorbornenium cations of the type [(Me3Si)(2)NP(C6H8)X][GaCl4] (X = Cl, N-3, 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.