Acta Crystallographica Section B

Structural Science

Volume 54, Part 4 (August 1998)

research papers

Acta Cryst. (1998). B54, 417-423 [ doi:10.1107/S0108768197020090 ]

Aminoguanidinium(2+) Hexafluorozirconate Monohydrate: A Co-Product of Preparing the Ferroelectric Anhydrous Salt

C. R. Ross II, B. L. Paulsen, R. M. Nielson and S. C. Abrahams

Abstract: Preparation of anhydrous aminoguanidinium(2+) hexafluorozirconate, CN₄H₈ZrF₆, shown previously to satisfy the structural criteria for ferroelectricity [Abrahams et al. (1996). Acta Cryst. B52, 806-809], generally results in the co-formation of a series of related fluorozirconates. The structure of the monohydrate salt, one of the co-products, has been redetermined to improve understanding of the preparation pathway, locate the H atoms and compare corresponding atom positions [Gerasimenko et al. (1989). Koord. Khim. 15, 130-135]. The positions of the H atoms were not established in the latter study. All 16 H atoms in the two symmetry-independent CN₄H₈(2+) ions are now located and refined, with R₁ = 0.0299 and S = 1.119. Both independent water molecules are disordered. Normal probability analysis reveals uncompensated error and/or underestimated uncertainty associated with ten non-H-atom position coordinates. The relative concentrations of HF, CN₄H₇Cl and H₂ZrF₆ are among the major variables controlling the formation of the related fluorozirconates.