Crystal Structure Of Hydroxohafnates Na2hf(Oh)(6) And K2hf(Oh)(6)

X-ray study of Na2Hf(OH)(6) (I) and K2Hf(OH)(6) (II) single crystals have been performed. In the rhombohedral structure of compound I, Hf and Na atoms possess the distorted octahedral coordination with the distances: Hf-O 2.08 Angstrom and Na-O 2.42-2.45 Angstrom. In the orthorhombic structure of compound II, there are two types of distorted octahedra-HfO6 (Hf-O 2.06-2.09 Angstrom) and eight-vertex KO8-polyhedra (K-O 2.75-3.17 Angstrom). The HfO6-octahedra are bound by a system of hydrogen bonds with the O ... O distances ranging within 2.80-2.85 Angstrom. The results of indexing of the powder diffraction patterns of compounds I and II are also given.