The crystal structure of the monoclinic Fe2(SO4)3

The crystal structure of the monoclinic Fe 2 (SO 4 ) 3 has been determined using three-dimensional intensities, measured with an automated Philips PW 1 100 single-crystal diffractometer. The structure was essentially obtained from the three-dimensional Patterson synthesis by applying the minimum function. The cell constants, obtained by least-squares from direct θ -value measurements on the diffractometer, are: a = 8.2955, b = 8.5332, c = 11.6304 Å, β = 90.25°; Z = 4; the space group is P 2 1 / n . Atomic parameters and anisotropic temperature factors wore refined by least-squares to R = 0.038. Corrections for anomalous dispersion and secondary extinction were applied. There are three different and almost regular SO 4 tetrahedra in the asymmetric unit of the cell. The S–O distances are virtually equal, their average values in the three tetrahedra being 1.468, 1.466 and 1.466 Å respectively. The corresponding average O–O distances are 2.397, 2.394 and 2.394 Å and the tetrahedral bond angles deviate from the ideal value 109.46° by less than 2.5°. The two Fe atoms in the asymmetric unit are octahedrally coordinated. Both of the FeO 6 octahedra are only slightly distorted. The average Fe–O distances in the two octahedra are 1.980 Å and 1.994 Å respectively, whereas the corresponding average O–O distances are 2.800 Å and 2.822 Å. All the coordination polyhedra are isolated. The SO 4 tetrahedra share each of their vortices with a FeO 6 octahedron, thus forming a three-dimensional network of tetrahedra and octahedra, in which each O atom is bonded to only one S and one Fe atom.