Crystal structure of cis-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N)bis-(thio-cyanato-κN)chromium(III) bromide from synchrotron X-ray diffraction data.

Dohyun Moon,Jong-Ha Choi

doi:10.1107/s2056989021001055

Abstract

The crystal structure of the title complex, cis-[Cr(NCS)2(cyclam)]Br (cyclam = 1,4,8,11-tetra-aza-cyclo-tetra-decane, C10H24N4), has been determined from synchrotron X-ray data. The asymmetric unit contains one [Cr(NCS)2(cyclam)]+ cation and one bromide anion. The CrIII ion of the complex cation is coordinated by the four N atoms of the cyclam ligand and by two N-coordinating NCS groups in a cis arrangement, displaying a distorted octa-hedral coordination sphere. The Cr-N(cyclam) bond lengths are in the range 2.075 (3) to 2.081 (3) Å while the average Cr-N(NCS) bond length is 1.996 (16) Å. The macrocyclic cyclam moiety adopts the most stable cis-V conformation. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the cyclam N-H groups as donor groups, and the bromide anion and the S atom of one of the NCS ligands as acceptor groups.

Highlights

The crystal structure of the title complex, cis-[Cr(NCS)2(cyclam)]Br, has been determined from synchrotron X-ray data
The CrIII ion of the complex cation is coordinated by the four N atoms of the cyclam ligand and by two N-coordinating
The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N—H groups as donor groups, and the bromide anion and the S atom of one of the NCS ligands as acceptor groups

Summary

Chemical context

Compounds containing cyclam (1,4,8,11-tetraazacyclotetradecane, C10H24N4) or its derivatives have a potential inhibitory effect on the replication of the human immunodeficiency virus (HIV) and have the ability to mobilize hematopoietic progenitor stem cells from the bone marrow into the blood (Ronconi & Sadler, 2007; De Clercq, 2010; Ross et al, 2012). Knowledge of the conformation for the macrocyclic ligand including various counter-anions are important factors in developing new highly effective anti-HIV drugs (Ronconi & Sadler, 2007; De Clercq, 2010; Ross et al, 2012). As an extension of our investigations on the coordination chemistry and conformations of CrIII complexes containing the cyclam ligand, one auxiliary bidentate or two monodentate ligands and various anions (Choi et al, 2004a,b; Choi & Lee, 2009; Subhan et al, 2011; Moon et al, 2013, 2017; Moon & Choi, 2021), we describe here the synthesis of a new salt complex, [Cr(NCS)2(cyclam)]Br, (I) and its structural characterization by synchrotron single-crystal X-ray diffraction

Structural commentary

Database survey

Synthesis and crystallization

Findings

Refinement