Crystal structure of bis[cis-(1,4,8,11-tetraazacyclotetradecane-κ4N)bis(thiocyanato-κN)chromium(III)] dichromate monohydrate from synchrotron X-ray diffraction data

Abstract

The structure of the complex salt,cis-[Cr(NCS)2(cyclam)]2[Cr2O7]·H2O (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron data. The asymmetric unit comprises of one [Cr(NCS)2(cyclam)]+cation, one half of a Cr2O72−anion (completed by inversion symmetry) and one half of a water molecule (completed by twofold rotation symmetry). The CrIIIion is coordinated by the four cyclam N atoms and by two N atoms ofcis-arranged thiocyanate anions, displaying a distorted octahedral coordination sphere. The Cr—N(cyclam) bond lengths are in the range 2.080 (2) to 2.097 (2) Å while the average Cr—N(NCS) bond length is 1.985 (4) Å. The macrocyclic cyclam moiety adopts thecis-V conformation. The bridging O atom of the dichromate anion is disordered around an inversion centre, leading to a bending of the Cr—O—Cr bridging angle [157.7 (3)°]; the 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 donor groups, and the O atoms of the Cr2O72−anion and water molecules as acceptor groups, giving rise to a three-dimensional network.