AbstractTheN,N,N′‐trimethylethylenediaminetetrafluorophosphate,4, was formed in the unusual reaction ofN,N,N′‐trimethyl‐N′‐trimethylsilylethylenediamine,1, with the NP‐bonded tetrafluorophosphoranes, dimethylaminotetrafluorophosphorane,2, or morpholinotetrafluorophosphorane,3. There was no evidence for the cleavage of a PF bond in the tetrafluorophosphoranes (with formation of Me3SiF); instead, the SiN compounds, R2NSiMe3(R2= Me2or O(CH2CH2)2) were formed. The19F and31P NMR spectra of4at room temperature indicated dynamic behavior. The X‐ray crystal structure analysis of4revealed the presence of a five‐membered ring, formally as a result of intramolecular donor–acceptor interaction (PN = 196.5 pm) between the nitrogen atom o