Crystal structure of bis-[trans-di-chlorido-bis(propane-1,3-di-amine-κ2N,N')chromium(III)] dichromate from synchrotron data.

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The structure of the title compound, [CrCl2(tn)2]2[Cr2O7] (tn = propane-1,3-di-amine; C3H10N2), has been determined from synchrotron data. The asymmetric unit contains one CrIII complex cation and half a [Cr2O7]2- anion. In the complex cation, the CrIII ion is coordinated by the four N atoms of two propane-1,3-di-amine (tn) ligands in the equatorial plane and by two Cl atoms in a trans configuration, displaying a distorted octa-hedral coordination sphere. The two six-membered rings in the complex cation have an anti chair-chair conformation with respect to each other. The mean Cr-N(tn) and Cr-Cl bond lengths are 2.09 (1) and 2.320 (2) Å, respectively. The slightly bent dichromate anion is disordered over two sets of sites (occupancy ratio = 0.7:0.3) and has a staggered conformation. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the NH2 groups of the tn ligands as donors and the O atoms of the [Cr2O7]2- anion and chlorido ligands as acceptors.