IR-absorption spectra of M2AF6hexafluorocomplexes (M-Na, K, Rb, Cs and NH4; A=Si, Ge, Sn) were obtained and intergrated intensities of bands assigned to stretching vibrations of AF6ions were measured. The reasons for the influence of exchange of the central atom and an outer-sphere cation on the intergrated intessities of vibration bands are discussed. It was found that the ammonium ion does not fit into the earlier established pattern of intensity dependence on cation size. Analysis of the frequencies v3(AF6) suggeste that this is coused by the presence in (NH4)2AF6of hydrogen bonds N-H F of different strength.