Investigation of hydrofluorides of the alkaline earth metals by the NMR method

Summary The structure of hydrofluorides with the composition MeF₂ · HF(Me=Sr, Ba) includes two anions: F^– and HF₂ ^– with a linear hydrogen bond. In SrF₂ · HF, the hydrogen bond is characterized by a more asymmetrical position of the proton than in BaF₂ · HF.Increasing the number of added HF molecules leads to the formation of two bifluoride ions in the compounds CaF₂ · 2HF and SrF₂ · 2.5HF. The hydrogen bond in this case is also nonsymmetrical, and the average F–H distance is equal to 1.17 A. Thus, the hydrogen bond in these compounds is of the same order as in KF · 2HF (r_F–F=2.33 A) 12],i.e., weaker than in KF · HF (r_F–F=2.26 A) 13], but stronger than in solid HF (r_F–F=2.49 A) 14].A structure with two polyfluoride anions evidently corresponds to the compound BaF₂ · 3HF.Institute of Inorganic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 9, No. 2, pp. 202–206, March–April, 1968.