Spectroscopic and structural studies of difluorophosphoryl azide F2P(O)N3, difluorophosphoryl isocyanate F2P(O)NCO, and difluorophosphoric acid anhydride, F2(O)POP(O)F2.

Difluorophosphoryl azide, F(2)P(O)N(3), was fully characterized by (19)F, (31)P, (14)N, and (15)N NMR, as well as by IR (gas, Ar-matrix), and Raman (liquid, solid) spectroscopy. For comparison the vibrational spectra of the isoelectronic difluorophosphoryl isocyanate, F(2)P(O)NCO was also studied. Both molecules were found to exist as single rotamers in the gas, liquid, and solid states. Their solid-state structures were determined by X-ray crystallography as the rotamers with the P=O bond being cis to the pseudohalide groups (with respect to the P-N bond). The F(2)P(O)N(3) molecule exhibits approximate C(s) symmetry (phi(O1P1-N1N2) = -0.7(3) degrees), while F(2)P(O)NCO is significantly distorted from C(s) symmetry (phi(O1P1-N1C1) = -18.9(5) degrees) because of intermolecular C...O contacts. The crystal structure of difluorophosphoric acid anhydride, F(2)(O)POP(O)F(2), was also determined, possessing crystallographic C(2) symmetry with the two F(2)PO groups slightly staggered by 10.66(7) degrees along the P...P vector, and a P-O-P angle of 140.89(10) degrees for the bridging oxygen atom. The experimental results are supported by quantum chemical calculations, and the conformational properties of F(2)P(O)N(3) and F(2)P(O)NCO are discussed.