Crystal structure of cis-di-chlorido-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4N)chromium(III) (oxalato-κ2O1,O2)(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4N)chromium(III) bis(perchlorate) from synchrotron data.

Dohyun Moon,Jong-Ha Choi

doi:10.1107/s2056989016014134

Abstract

In the asymmetric unit of the title compound, [CrCl2(C10H24N4)][Cr(C2O4)(C10H24N4)](ClO4)2 (C10H24N4 = 1,4,8,11-tetra-aza-cyclo-tetra-decane, cyclam; C2O4 = oxalate, ox), there are two independent halves of the [CrCl2(cyclam)]+ and [Cr(ox)(cyclam)]+ cations, and one perchlorate anion. In the complex cations, which are completed by application of twofold rotation symmetry, the CrIII ions are coordinated by the four N atoms of a cyclam ligand, and by two chloride ions or one oxalate bidentate ligand in a cis arrangement, displaying an overall distorted octa-hedral coordination environment. The Cr-N(cyclam) bond lengths are in the range of 2.075 (5) to 2.096 (4) Å while the Cr-Cl and Cr-O(ox) bond lengths are 2.3358 (14) and 1.956 (4) Å, respectively. Both cyclam moieties adopt the cis-V conformation. The slightly distorted tetra-hedral ClO4- anion remains outside the coordination sphere. The supra-molecular architecture includes N-H⋯O and N-H⋯Cl hydrogen bonding between cyclam NH donor groups, O atoms of the oxalate ligand or ClO4- anions and one Cl ligand as acceptors, leading to a three-dimensional network structure.

Highlights

In the complex cations, which are completed by application of twofold rotation symmetry, the
The Cr—N(cyclam) bond lengths are in the range of 2.075 (5) to 2.096 (4) Å while the Cr—Cl and
The Cr—N bond lengths from the donor atoms of the cyclam ligands are in the range of 2.075 (5) to

Summary

Chemical context

Transition metal complexes with cyclam (1,4,8,11-tetraazacyclotetradecane, C10H24N4) ligands can adopt both planar (trans) and folded (cis) configurations (Poon & Pun, 1980). The most stable conformation cannot fold to give the cis-III complex as this requires the diagonal NH groups to both lie above or below the plane of the macrocycle. Knowledge of the conformation and crystal packing of transition metal complexes containing the cyclam ligand has become important in the development of new highly effective anti-HIV drugs that specially target alternative events in the HIV replicative cycle (De Clercq, 2010). In this communication, we report on the synthesis and structural characterization of a new double complex,

Structural commentary

Supramolecular features

Database survey

Synthesis and crystallization

Refinement