Crystal structure and spectroscopic properties of aquadichlorido{1,1′-[(pyridine-2,6-diyl-κN)bis(methylene)]bis(4-butyl-4,5-dihydro-1H-1,2,4-triazole-5-thione-κN2)}cobalt(II)

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 nitrogen atoms (two triazole and one pyridine). The ligand is ambidentate and can coordinate via three nitrogen atoms or two sulfur and one nitrogen atoms. The cobalt(II) metal center has pseudo-octahedral 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 molecule 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 molecule 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 interaction with a chlorine ion, forming one intermolecular interaction with the pincer group and a water molecule and a second intramolecular interaction with a C—H group within the pincer group. Crystal packing is also highlighted with C22(6)>aa>a ring motifs, forming a three-dimensional supramolecular network structure. While some stacking of the pyridine rings in the unit cell is observed, there are no relevant π–π interactions 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 molecule and one chloride ligand from the complex. In the future, we plan to screen this cobalt(II) complex for electrocatalysis reactivity.

Keywords

• crystal structure
• electrospray mass spectrum
• nmr
• cobalt(ii)
• pincer complex