Preparation and Crystal Structure of Na2Zn(HPO4)2 · 4H2O, a New Layered Sodium Zinc Phosphate Containing "Bifurcated" Tetrahedral 12-Rings

Abstract

We report the low-temperature (∼0°C) synthesis and X-ray single-crystal structure of Na2Zn(HPO4) · 4H2O, a new layered material, whose structure is built up from sheets of vertex-sharing ZnO4 and HPO4 tetrahedra, which encapsulate octahedrally coordinated "guest" sodium cations and water molecules. The Zn/P tetrahedral-atom connectivity in Na2Zn(HPO4)2 · 4H2O results in a two-dimensional network of layers of "bifurcated," tetrahedral 12-rings, with interlayer connectivity established only by sodium cations and via H bonds. X-ray powder data and 31P MAS NMR spectra are consistent with those expected from the crystal structure data. Crystal data are Na2Zn(HPO4)2 · 4H2O (ZnNa2P2O12H10), Mr = 375.37, monoclinic, space group P 21/c (No. 14), a = 8.947(2) Å b = 13.254(2) Å, c = 10.098(2) Å, β = 116.358(6)°, V = 1074.5 Å3, Z = 4, R = 4.25%, and Rw = 5.68% [1608 unique reflections with I > 3σ(I)].