Keywords: FHF− or HF2−, hydrogen(difluoride) anion or bifluoride; M, metal; F, fluoride; TM, transition metal; dmpe, 1,2-bis(dimethylphosphino)ethane; dcpe, bis(dicyclohexylphosphino)ethane; PMe3, trimethylphosphine; tBu-bpy, 4,4′-di-tert-butyl-2,2′-dipyridyl; NFSI