Coordination preferences of NNO and NNS Schiff base ligands with Co(III) complexes: Synthesis, characterization and DFT calculation

Abstract

Two Co(III) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1 ligand, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) and the condensation product of 2-acetylpyridine and Girard's P reagent (HL2Cl ligand, (E)-1-(2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethyl)pyridin-1-ium chloride) have been synthesized and characterized based on the results of single-crystal X-ray diffraction, NMR and IR spectroscopy and elemental analysis. Cobalt(III) complex with HL1 ligand, [Co(L1)2]BF4⋅H2O (1), is bis octahedral complex in which two deprotonated ligand molecules coordinate in a mer arrangement through two NNS sets of donor atoms. In cobalt(III) complex with HL2Cl, [Co(L2)(N3)3] (2), the ligand is coordinated in deprotonated, formally neutral, form to Co(III) ion in tridentate fashion through NNO set of donor atoms, and the other three coordination sites of a monokis octahedron are occupied by meridionally coordinated azide anions. DFT calculations were performed to elucidate coordination preferences of these ligands toward Co(III) ion.