The present work deals with the use of the adduct Et3N·nHF as fluorination agent for heteroatom bridged phosphorus compounds of the structure X2P(O)NPX3 (I) (XCl, Ph, PhO, EtO, NEt2) and X2P(O)YP(O)X2 (II) (XCl, PhO, EtO, NEt2; YNH, NMe, O). Facilities and limits of the substitution of fluoride for phosphorus-bonded groups X are shown.
The mechanism of the reaction and therewith the type of resulting products depends on the concentration of protons in the reaction medium as well as the concentration and nucleophilic force of the free fluoride ions. Furthermore, the temperature, the base used and the presence of other nucleophiles competing with fluoride play an important role.
Both N-phosphoryl phosphazenes (I; XCl, Ph, PhO, NEt2) and imidodiphosphoric acid derivatives (II; X=Cl, PhO; YNH) give defined X/F replacement products. Under certain conditions pentafluorophosphates of the structure [F5P-Y-P(O)X2]− (XCl, PhO, F; YNH, O) may be obtained from N-phosphoryl phosphazenes (I; XCl, PhO) and pyrophosphoryl chloride (II; XCl; YO).
All reactions were studied by means of NMR spectroscopy (1H, 19F, 31P). The mechanism of the fluoridolysis is discussed.