Crystal structure refinement of bifluorides MHF2 (M = Na, NH4, Rb).: Crystal structures of Rb5F4(HF2) • 2H2O and RbF • H2O

The crystal structures of alkali metal and ammonium bifluorides MHF2 (M = Na, NH4, or Rb) are refined using single-crystal X-ray diffraction. In all the crystals of acid fluorides studied, HF2- anions have a linear structure with F center dot center dot center dot F distances ranging from 2.277 to 2.281 angstrom. The crystal structures of the Rb5F4(HF2) 2H(2)O and RbF center dot H2O compounds are determined. It is established that, in these structures, the O-H center dot center dot center dot F hydrogen bonds whose lengths are equal to 2.55-2.57 and 2.63 angstrom participate in the formation of trinuclear bent anions and zigzag anionic chains, respectively. (C) 2005 Pleiades Publishing, Inc.