Crystal structure of trans-dichlorido(1,4,8,11-tetraazacyclotetradecane- κ4N)chromium(III) bis(formamide- κO)(1,4,8,11-tetraazacyclotetradecaneκ 4N)chromium(III) bis[tetrachloridozincate(II)].

The structure of the title compound, [CrCl2(C10H24N4)][Cr(HCONH2)2- (C10H24N4)][ZnCl4]2 (C10H24N4 = 1,4,8,11-tetraazacyclotetradecane, cyclam; HCONH2 = formamide, fa), has been determined from synchrotron X-ray data. The asymmetric unit contains two independent halves of the [CrCl2(cyclam)]+ and [Cr(fa)(cyclam)]3+ cations, and one tetrachloridozincate anion. In each complex cation, the CrIII ion is coordinated by the four N atoms of the cyclam ligand in the equatorial plane and two Cl ligands or two O-bonded formamide molecules in a trans axial arrangement, displaying a distorted octahedral geometry with crystallographic inversion symmetry. The Cr-- N(cyclam) bond lengths are in the range 2.061 (2) to 2.074 (2) A ° , while the Cr--Cl and Cr--O(fa) bond distances are 2.3194 (7) and 1.9953 (19) A ° , respectively. The macrocyclic cyclam moieties adopt the centrosymmetric trans-III conformation with six- and five-membered chelate rings in chair and gauche conformations. The crystal structure is stabilized by intermolecular hydrogen bonds involving the NH or CH groups of cyclam and the NH2 group of coordinated formamide as donors, and Cl atoms of the ZnCl4 2- anion as acceptors. [ABSTRACT FROM AUTHOR]