Abstract
Iron tri(hydrogenphosphite), Fe(HPO3H)(3), crystallizes in both a monoclinic and a hexagonal space group. In this report the structure determination of the hexagonal variant is described: space group P6(3), a = 8.1690(2) Angstrom, c = 6.9300(2) Angstrom. The structure is slightly disordered, Fe3+ being partially replaced by Al3+, and is very close to that of Fe-2(HPO3)(3). The only significant difference is that one half of the FeO6 octahedra is missing and that its density is reduced by one half.