Crystal structure of hexa­kis­(N,N-di­methyl­form­amide-κO)iron(III) μ-chlorido-bis­(tri­chlorido­cadmium)

The title compound, [Fe(C3H7NO)6][Cd2Cl7], crystallizes in the trigonal space group RUnlabelled Image and is assembled from discrete [Fe(DMF)6]3+ cations (DMF = N,N-di­methyl­formamide) and [Cd2Cl7]3− anions. In the cation, the iron(III) atom, located on a special position of Unlabelled Image site symmetry, is coordinated by six oxygen atoms from DMF ligands with all Fe—O distances being equal [2.0072 (16) Å]. A slight distortion of the octa­hedral environment of the metal comes from the cis O—Fe—O angles deviating from the ideal value of 90° [86.85 (7) and 93.16 (7)°] whilst all the trans angles are strictly 180°. The central Cl atom of the [Cd2Cl7]3− anion is also located on a special position of Unlabelled Image site symmetry and bridges two corner sharing, tetra­hedrally coordinated CdII atoms. The two Cd atoms and the central Cl atom are colinear. The two sets of terminal chloride ligands on either side of the dumbbell-like anion are rotated relative to each other by 30°. In the crystal, the cations and anions, stacked one above the other along the c-axis direction, are held in place principally by electrostatic inter­actions. There are also C—H⋯Cl and C—H⋯O inter­actions, but these are rather weak. Of the six crystal structures reported to date for ionic salts of [Fe(DMF)6]n+ cations (n = 2, 3), five contain FeII ions. The title compound is the second example of a stable compound containing the [Fe(DMF)6]3+ cation. The existence of both [Fe(DMF)6]2+ and [Fe(DMF)6]3+ cations shows that the DMF ligand coordination sphere can accommodate changes in the charge and spin states of the metal centre.