Na[GeF₅]·2HF: the first quarternary phase in the H–Na–Ge–F system

The structure of cis - or trans -bridged [GeF 5 ] − anionic chains have been investigated [Mallouk et al. (1984). Inorg. Chem. 23 , 3160–3166] showing the first crystal structures of μ-F-bridged pentafluorogermanates. Herein, we report the second crystal structure of trans -pentafluorogermanate anions present in the crystal structure of sodium trans -pentafluorogermanate(IV) bis(hydrogen fluoride), Na[GeF 5 ]·2HF. The crystal structure [orthorhombic Pca 2 1 , a = 12.3786 (3), b = 7.2189 (2), c = 11.4969 (3) Å and Z = 8] is built up from infinite chains of trans -linked [GeF 6 ] 2− octahedra, extending along the b axis and spanning a network of pentagonal bipyramidal distorted Na-centred polyhedra. These [NaF 7 ] polyhedra are linked in a trans -edge fashion via hydrogen fluoride molecules, in analogy to already known sodium hydrogen fluorides and potassium hydrogen fluorides.