Proazaphosphatranes, also known as Verkade's superbases, are among the strongest nonionic bases available. Their extreme basicity derives in part from their ability to form a P-N transannulation upon interaction of the P atom with an electrophile. Although haloazaphosphatrane cations of the form [XP(RNCH2CH2)(3)N](+) have previously been reported for X = Cl, Br, and I, no fluoroazaphosphatranes (X = F) have been prepared. Unlike treatment with Cl-2, Br-2, I-2, and surrogates thereof, reaction of proazaphosphatranes with XeF2 results in decomposition. Analysis of the decomposition products suggested that fluoride ions may be the destructive agent. However, oxidation of a proazaphosphatrane/BPh3 frustrated Lewis pair affords [FP(RNCH2CH2)(3)N] [FBPh3]. Systematic trends in the experimental and computed NMR and structural data are considered. A computational analysis suggests that the transannular P-N distance varies as a result of the flexibility of the molecules and their capacity to deform in the solid state.