Crystal structure determination of Zr(OH) 2(NO 3) 2 · 4.7H 2O from X-ray powder diffraction data

Abstract

The crystal structure of Zr(OH) 2(NO 3) 2 · 4.7H 2O has been solved ab initio from X-ray powder data obtained from a conventional diffractometer. The unit cell was obtained by means of the successive dichotomy indexing method. This is triclinic, space group P 1 with the following lattice parameters: a = 9.541(1) Å, b = 9.590(1) Å, c = 6.753(1) Å, α = 98.64(1)°, β = 92.89(1)° and γ = 118.60(1)°, Z = 2. A total of 136 integrated intensities, unambiguously indexed, were used to generate a Patterson function from which the approximate heavy atom coordinates were derived. The remaining atoms were located by an interpretation of successive three-dimensional Fourier maps. The structure was refined by means of the Rietveld method ( R F = 0.039, R B = 0.063, R p = 0.084 and R wp = 0.108). In accordance with the chemical analysis, the structure model shows that the most probable number of water molecules is 4.7. The structure of Zr(OH) 2(NO 3) 2 · 4.7H 2O consists of infinite and isolated chains of trigonal dodecahedra sharing edges. The zirconium atom is eightfold coordinated by four OH groups, two water molecules, and one bidentate nitrate group. The chains are held together by hydrogen bonds through additional water molecules and nitrate groups located between the chains.