Synthesis and characterizations of fluorophosphoryl diazide and diisocyanate

Abstract

Two fluorine-substituted phosphoryl pseudohalides including the highly explosive diazide FP(O)(N3)2 and diisocyanate FP(O)(NCO)2 have been synthesized and fully characterized with IR (gas-phase and noble-gas matrices), Raman (liquid), and NMR (19F and 31P) spectroscopy. The vibrational spectra of FP(O)(N3)2 and FP(O)(NCO)2 were analyzed with the aid of the B3LYP/6−311+G(3df) calculations, and the assignments were made in terms of a mixture of syn-syn and anti-syn conformers, in which the two pseudohalogen groups (N3 and NCO) adopt syn/anti configuration to the P=O bond with respect to the P–N bonds. The low-temperature X-ray crystallographic structure of FP(O)(NCO)2 in the solid state reveals molecular Cs symmetry with a syn-syn conformation (ϕ(O1P1–N1C1) = 54.80(15)°) and weak intermolecular O⋯C contacts (2.901(2) Å). In line with the experimental observation of dominant syn-syn conformers for gaseous FP(O)(N3)2 and FP(O)(NCO)2, calculations at the CCSD(T)/aug-cc-pVTZ//B3LYP/6−311+G(3df) level demonstrate that the anti-syn conformers are higher in energy (ΔG) by 3.8 and 3.2 kJ mol–1, respectively.