Abstract
The structure of the title compound, [Cr(NCS)2(C2H8N2)2]ClO4, has been determined from synchroton data. The asymmetric unit consists of one half of a centrosymmetric Cr(III) complex cation and half of a perchlorate anion with the Cl atom on a twofold rotation axis. The Cr(III) ion is coordinated by the four N atoms of two ethane-1,2-di-amine (en) ligands in the equatorial plane and two N-bound thio-cyanate (NCS(-)) anions in a trans-axial arrangement, displaying a slightly distorted octa-hedral geometry with crystallographic inversion symmetry. The Cr-N(en) bond lengths are in the range 2.053 (16)-2.09 (2) Å, while the Cr-N(thio-cyanate) bond length is 1.983 (2) Å. The five-membered en rings are disordered over two sites, with occupancy ratios of 0.522 (16):0.478 (16). Each ClO4 (-) anion is disordered over two sites with equal occupancy. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the en NH2 groups as donors and perchlorate O and thio-cyanate S atoms as acceptors.
Highlights
The structure of the title compound, [Cr(NCS)2(C2H8N2)2]ClO4, has been determined from synchroton data
The CrIII ion is coordinated by the four N atoms of two ethane-1,2-diamine ligands in the equatorial plane and two N-bound thiocyanate (NCS) anions in a trans-axial arrangement, displaying a slightly distorted octahedral geometry with crystallographic inversion symmetry
The crystal structure is stabilized by intermolecular hydrogen bonds involving the en NH2 groups as donors and perchlorate O and thiocyanate S atoms as acceptors
Summary
Considerable attention has been focussed for some time on metal complexes containing thiocyanate ligands because of their ability to coordinate through either the N or S atoms. The [Cr(NCS)2(en)2]+ cation can form either trans or cis geometric isomers. Trans and cis isomers of the complex cation with SCN or ClO4 counter-anions have been prepared and their IR spectral properties reported (House, 1973; Sandrini et al, 1978; De et al, 1987). IR and electronic spectral properties are useful in determining the geometric isomers of chromium(III) complexes with mixed ligands (Choi, 2000; Choi et al, 2004; Choi & Moon, 2014). To compare and contrast this structure with a complex of this cation with a different counter-anion we report here the structure of trans-[Cr(NCS)2(en)2]ClO4, (I). The ClO4 counter-anion lies well outside the coordination sphere of the complex and, because of significant disorder, the tetrahedral geometry of this anion is severely distorted
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