The Crystal Structure of “Dichrochloride”, [Co(NH3)3H2OCl2]Cl

Abstract

An X-ray diffraction study of crystals of dichloro-aquo-triammine-cobalt (III) chloride eads to a hexagonal unit of structure with a=7.37 A. and c=8.75 A., containing two formula units in it. The most probable space group is D_6h⁴−C6/mmc. For an accurate determination of the structure, the method of three dimensional Fourier series was used. The determined structure is most easily described as NiAs type, consisting of [Co(NH₃)₃H₂OCl₂]⁺ and Cl⁻ ions. Two chlorine atoms are coordinated to a cobalt atom in trans-positions with respect to each other, each being 2.33 A. from the cobalt atom. The Cl-Co-Cl direction being parallel to the c-axis, the octahedral complex ions seem to have statistical azimuthal orientations in the crystal and the apparent, symmetry of the complex ion is D_3h− 6m2. Such an arrangement of the complex ions in the crystal may well account for the marked red-blue dichroism of the crystals.