A Symmetric F−H−F Hydrogen Bond in Strontium Bifluoride, Sr[HF₂]₂

Abstract

Single crystal X-ray diffraction shows the hydrogen bond within the [FÀ HÀ F] À anion of Sr[HF 2 ] 2 to be symmetric with HÀ F bond lengths of 1.143(5) Å and an intramolecular F•••F distance of 2.2826(18) Å. The [HF 2 ] À anion adopts crystallographic C 2symmetry, however, it is essentially linear with a FÀ HÀ F angle of 174(4)°. Solid-state quantum chemical calculations agree with the experimental findings, showing a slightly bent FÀ HÀ F angle of 177.8°. The decomposition of Sr[HF 2 ] 2 to SrF 2 and HF is endothermic by + 64 kJ/mol at room temperature. The bonding in the [FÀ HÀ F] À anion is clearly ionic both in the solid state and gas phase.