Crystal structure of bis-[bis-(1,4,7-tri-aza-cyclo-nonane-κ3 N,N',N'')chromium(III)] tris-(tetra-chlorido-zincate) monohydrate from synchrotron X-ray data.

The structure of the title compound, [Cr(tacn)2]2[ZnCl4]3·H2O (tacn is 1,4,7-tri-aza-cyclo-nonane; C6H15N3), has been determined from synchrotron X-ray data. Each CrIII cation is coordinated by the six N atoms from the two tacn ligands, displaying a distorted octa-hedral geometry. Three distorted tetra-hedral [ZnCl4]2- anions and one lattice water mol-ecule lie outside this coordination sphere. The Cr-N bond lengths are in the range 2.0621 (11) to 2.0851 (12) Å, while the mean inner N-Cr-N bond angle is 82.51 (5)°. The crystal packing is stabilized by hydrogen-bonding inter-actions with the N-H groups of the tacn ligands and the water O-H groups acting as donors, and the O atoms of the water mol-ecules and Cl atoms of the [ZnCl4]2- anions as acceptors. Overall these contacts lead to the formation of a three-dimensional network.