F-19, N-14 AND N-15 NMR SPECTROSCOPIC STUDIES ON TRIAZADIENYL FLUORIDE, N3F

The results of F-19, N-14 and N-15 NMR measurements for all N-14/N-15 isotopomers of N3F in CD2Cl2 solution are reported. Substantial deshielding for the N-alpha and N-gamma atoms, relative to other covalent azides XN3 (X = Cl, H, CF3, etc.), is observed. The coupling constants also indicate unusual bonding in N3F. 1J(N-15-alpha, F) and 3J(N-15-gamma, F) are similar (58.2 and 58.6 Hz, respectively), very small for a 1J((NF)-N-15) but very large for a 3J((NF)-N-15) value. The observed value of 26.5 Hz for 1J(N-15-alpha N-15-beta) is the largest, and 2J(N-15-alpha N-15-gamma) (5.3 Hz) is the first reported coupling constant for an azide. The unusual N3F NMR data are discussed in terms of calculated atomic charges and the influence of the paramagnetic term which dominates the chemical shifts. This term expresses the deshielding due to the circulation of electrons in the magnetic field between the HOMOs and the LUMOs.