Hydrate isomerism in [Cu(en)2(H2O)1.935]2[Fe(CN)6].4H2O.

Abstract

The title compound, bis[di­aqua­bis­(ethyl­enedi­amine-κ2N,N′)copper(II)­] hexa­cyano­iron(II) tetrahydrate, [Cu(C2H8N2)2(H2O)1.935]2[Fe(CN)6]·4H2O, was crystallized from an aqueous reaction mixture initially containing CuSO4, K3[Fe(CN)6] and ethyl­enedi­amine (en) in a 3:2:6 molar ratio. Its structure is ionic and is built up of two crystallographically different cations, viz. [Cu(en)2(H2O)2]2+ and [Cu(en)2(H2O)1.87]2+, there being a deficiency of aqua ligands in the latter, [Fe(CN)6]4− anions and disordered solvent water mol­ecules. All the metal atoms lie on centres of inversion. The Cu atom is octahedrally coordinated by two chelate-bonded en mol­ecules [mean Cu—N = 2.016 (2) Å] in the equatorial plane, and by axial aqua ligands, showing very long distances due to the Jahn–Teller effect [mean Cu—O = 2.611 (2) Å]. In one of the cations, significant underoccupation of the O-atom site is observed, correlated with the appearance of a non-coordinated water mol­ecule. This is interpreted as the partial contribution of a hydrate isomer. The [Fe(CN)6]4− anions form quite regular octahedra, with a mean Fe—C distance of 1.913 (2) Å. The dominant intermolecular interactions are cation–anion O—H⋯N hydrogen bonds and these inter­actions form layers parallel to (001).