Aminodifluorophosphine: crystal and molecular structure at 95 K, and vibrational spectra of condensed phases

Abstract

The crystal and molecular structure of PF2(NH2) has been determined at 95 K. A single crystal was grown in situ on a Weissenberg goniometer and transferred to a CAD4 diffractometer for data collection. Crystals of PF2(NH2) are monoclinic, space group P21/c, with a= 5.2125(26), b= 12.830(5), c= 4.896(4)A, β= 115.07(6)°, and Z= 4. Two quadrants of data were collected and merged to give 1 300 reflections, of which 1 243 were considered to be above background. The final R was 0.0376. The P–N bond length is 1.6384(9)A, while the P–F(1)[1.6083(11)A] and P–F(2)[1.5899(6)A] distances are inequivalent and reflect the involvement of F(1) in intermolecular hydrogen bonding. The N is also hydrogen bonded and the intermolecular bonding gives rise to a corrugated layer of PF2(NH2) molecules. Infrared and Raman spectra of PF2(NH2) in the liquid, unannealed solid, and crystalline phases have also been recorded and analysed. Spectra of the crystalline solid, formed by a spontaneous annealing process at 110 K, are consistent with the crystal structure, showing shifts in N–H stretching frequencies, and at least one band, absent for non-crystalline phases, assigned to deformations of the hydrogen-bonding network. Stretching frequencies for N–H bonds in NHD species have been used to give accurate N–H bond lengths, and the combined X-ray and spectroscopic data allow the hydrogen-bonding contacts within the crystal, which determine the overall crystal packing, to be fully characterised.