Crystal structure of bis[(oxalato-κ2O1,O2)(1,4,8,11-tetraazacyclotetradecane-κ4N)chromium(III)] dichromate octahydrate from synchrotron X-ray data

• Main Authors: Dohyun Moon, Jong-Ha Choi
• Format: Article
• Language: English
• Published: International Union of Crystallography 2017-03-01
• Series: Acta Crystallographica Section E: Crystallographic Communications
• Subjects: crystal structure; cyclam; chromium(III) complex; bidentate oxalato ligand; cis-V conformation; dichromate anion; hydrogen bonding; synchrotron radiation
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S2056989017002614

The asymmetric unit of the title compound, [Cr(C2O4)(C10H24N4)]2[Cr2O7]·8H2O (C10H24N4 = 1,4,8,11-tetraazacyclotetradecane, cyclam; C2O4 = oxalate, ox) contains one [Cr(ox)(cyclam)]+ cation, one half of a dichromate anion that lies about an inversion centre so that the bridging O atom is equally disordered over two positions, and four water molecules. The terminal O atoms of the dichromate anion are also disordered over two positions with a refined occupancy ratio 0.586 (6):0.414 (6). The CrIII ion is coordinated by the four N atoms of the cyclam ligand and one bidentate oxalato ligand in a cis arrangement, resulting in a distorted octahedral geometry. The Cr—N(cyclam) bond lengths are in the range 2.069 (2)–2.086 (2) Å, while the average Cr—O(ox) bond length is 1.936 Å. The macrocyclic cyclam moiety adopts the cis-V conformation. The dichromate anion has a staggered conformation. The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N—H groups and water O—H groups as donors, and the O atoms of oxalate ligand, water molecules and the Cr2O72− anion as acceptors, giving rise to a three-dimensional network.