Thermal decomposition of a new compound, (N2H5)(2)VF5 . H2O, prepared from aqueous solutions, gives in inert atmosphere at 93 degrees C the new compound (N2H5)(2)VF5. The decomposition proceeds further over intermediates, N2H5VF4 at 236 degrees C and NH4VF4 at 268 degrees C, to the impure VF3 at 615 degrees C. According to the infrared spectra there are weak hydrogen bonds in all nitrogen compounds. There are different types of N2H5+ cations in (N2H5)(2)VF5 . H2O and (N2H5)(2)VF5. In N2H5VF4, the cation is coordinated over the lone pair of the vanadium atom. By analogy with the spectra of similar compounds, isolated octahedra [VF5 . H2O](2-) appear in the structure of (N2H5)(2)VF5 . H2O and fluorine-bridged chains of [VF4F2/2] octahedra in [N2H5](2)VF5.