Sodium dipotassium citrate, NaK2C6H5O7

Abstract

The crystal structure of sodium dipotassium citrate, Na+·2K+·C6H5O73-, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The Na+ and one of the K+ cations are six-coordinate, with bond-valence sums of 1.13 and 0.92 valence units, respectively, while another crystallographically independent K+ cation is seven-coordinate with a bond-valence sum of 1.20. The [KO6] and [KO7] polyhedra share edges and corners to form layers perpendicular to the b axis. The distorted [NaO6] octahedra share edges to form chains along the a axis. The result is a three-dimensional network. The only O-H⋯O hydrogen bond is an intramolecular one between the hydroxy group and a terminal carboxylate group.