Crystal structure of bis[trans-(1,4,8,11-tetraazacyclotetradecane-κ4N)bis(thiocyanato-κN)chromium(III)] tetrachloridozincate from synchrotron data

Abstract

The structure of the title compound, [Cr(NCS)2(cyclam)]2[ZnCl4] (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron data. The asymmetric unit contains two independent halves of the CrIII complex cations and half of a tetrachloridozincate anion. In each complex cation, the CrIII atom is coordinated by the four N atoms of the cyclam ligand in the equatorial plane and by two N-bound NCS− anions in a trans axial arrangement, displaying a distorted octahedral geometry with crystallographic inversion symmetry. The mean Cr—N(cyclam) and Cr—N(NCS) bond lengths are 2.065 (4) and 1.995 (6) Å, respectively. The macrocyclic cyclam moieties adopt centrosymmetric trans-III configurations with six- and five-membered chelate rings in chair and gauche configurations, respectively. The [ZnCl4]2− anion, which lies about a twofold rotation axis, has a slightly distorted tetrahedral geometry. The crystal packing is stabilized by hydrogen-bonding interactions between the N—H groups of the cyclam ligands, the S atoms of the NCS− groups and the Cl− ligands of the anion.

Keywords

• crystal structure
• synchrotron radiation
• cyclam
• thiocyanate ligand
• trans-III configuration
• chromium(III) complex
• hydrogen bonding