Crystal structure and spectroscopic properties of aqua-dichlorido-{1,1'-[(pyridine-2,6-diyl-κN)bis(methyl-ene)]bis-(4-butyl-4,5-di-hydro-1H-1,2,4-triazole-5-thione-κN 2)}cobalt(II).

Natalia R Bertolotti,Sheila C Bonitatibus,Tyler J Ostrowski,John R Miecznikowski,Kendra R Landy,Jerry P Jasinski,Allison N Smolinsky

doi:10.1107/s2056989020013547

Abstract

The structure of the title compound, [CoCl2(C19H27N7S2)(H2O)], at 173 K has monoclinic (C2/c) symmetry. We report here the synthesis, single-crystal structure, electrospray mass spectrum and NMR spectroscopy of a new six-coordinate cobalt(II) pincer complex. The pincer ligand, in this complex, which is novel, coordinates via three nitro-gen atoms (two triazole and one pyridine). The ligand is ambidentate and can coordinate via three nitro-gen atoms or two sulfur and one nitro-gen atoms. The cobalt(II) metal center has pseudo-octa-hedral geometry and based on the single-crystal structure, the pincer ligand coordinates in a meridional fashion with the metal and adjacent six-membered ring ligands all in a similar plane and forming two slightly distorted boat configurations. The other two coordinated monodentate ligands are one water mol-ecule and two chloride ions with four cobalt(II) complexes in the unit cell. The asymmetric unit of the complex is comprised of half the pyridine ring and water mol-ecule with the CoII atom at the center of the pincer situated about a twofold axis. The Co-N, Co-O, and Co-Cl bond lengths are consistent with single bonds. In the crystal, the complex forms a three-centre bifurcated weak hydrogen-bonding inter-action with a chlorine ion, forming one inter-molecular inter-action with the pincer group and a water mol-ecule and a second intra-molecular inter-action with a C-H group within the pincer group. Crystal packing is also highlighted with C 2 2(6)>a<a infinite chains forming along [001] supported by R 2 2(8)>a>a ring motifs, forming a three-dimensional supra-molecular network structure. While some stacking of the pyridine rings in the unit cell is observed, there are no relevant π-π inter-actions in the crystal packing. The 1H and 13C{1H} NMR spectra of the complex are consistent with a plane of symmetry being present. The electrospray mass spectrum, which was collected in positive ion mode, showed the loss of one water mol-ecule and one chloride ligand from the complex. In the future, we plan to screen this cobalt(II) complex for electrocatalysis reactivity.

Highlights

The structure of the title compound, [CoCl2(C19H27N7S2)(H2O)], at 173 K has monoclinic (C2/c) symmetry
The cobalt(II) metal center has pseudooctahedral geometry and based on the single-crystal structure, the pincer ligand coordinates in a meridional fashion with the metal and adjacent six-membered ring ligands all in a similar plane and forming two slightly distorted boat configurations
The asymmetric unit of the complex is comprised of half the pyridine ring and water molecule with the CoII atom at the center of the pincer situated about a twofold axis

Summary

Chemical context

Pincer ligands are tridentate ligands that coordinate to metal centers either in a meridional or facial manner (Peris & Crabtree, 2018; Gunanathan & Milstein, 2014). In 2012, Miecznikowski and co-workers reported the preparation of a pincer ligand precursor based on a bis-triazole starting material that could coordinate via sulfur, nitrogen, and sulfur donor atoms or via three nitrogen donor atoms (Miecznikowski et al, 2012). We wondered if the cobalt(II) metal center would coordinate to the pincer ligand via three nitrogen atoms as observed for the zinc(II) complex or via sulfur, nitrogen, and sulfur donor atoms. In this communication, we report the preparation, spectroscopic characterization, electrospray mass spectrometry, and single crystal structure of a cobalt(II) pincer complex that contains an ambidentate ligand (Fig. 2).

Structural commentary

Supramolecular features

Funding information