Syntheses and Crystal Structures of Sodium Hydrogen Fluorides NaF· n HF ( n = 2, 3, 4)

A series of higher sodium hydrogen fluorides were synthesized and structurally characterized. Sodium tetrahydrogen pentafluoride, NaH 4 F 5 , crystallizes in space group type I 4 1 / a with cell parameters a = 6.0275(4), c = 11.6208(13) Å, V = 422.19(7) Å 3 , Z = 4 at 100 K. Sodium trihydrogen tetrafluoride, NaH 3 F 4 , crystallizes in space group type R 3 with cell parameters a = 6.5139(4), c = 13.4040(15) Å, V = 492.55(8) Å 3 , Z = 6 at 100 K. Sodium dihydrogen trifluoride, NaH 2 F 3 , crystallizes in space group type Pnma with cell parameters a = 7.9276(9), b = 3.4514(3), c = 9.6937(10) Å, V = 265.23(5) Å 3 , Z = 4 at 100 K. The investigations were complemented by IR spectroscopy and theoretical calculations. NaH 2 F 3 was additionally characterized by means of powder neutron diffraction. All observed F–H ··· F hydrogen bonds are unsymmetric, close to linearity and can be considered as strong hydrogen bonds.