Cobalt(II) complexes with pentadentate Schiff bases 2,6-diacetylpyridine hydrazones: Syntheses and structures

Abstract

Seven new cobalt(II) complexes based on the Schiff bases, 2,6-diacetylpyridine bis(isonicotinoylhydrazone) (H2L1) and 2,6-diacetylpyridine bis(nicotinoylhydrazone) (H2L2), are synthesized and studied by X-ray diffraction analysis: [Co(H2L1)(NCS)2] · 2.25H2O (I), [Co(H2L2)(NCS)2] · CH3OH (II), [Co(H2L2)(NCS)(H2O)]NCS (III), [Co(H4L1)(NCS)2](NO3)2 · 2H2O (IV), [Co(H4L1)(NCS)2][Co(NCS)4] · 0.75H2O (V), [Co(H4L2)(NCS)2][Co(NCS)4] · 1.75H2O (VI), and [Co(H2L2)(NCS)(CH3OH)]2[Co(NCS)4] · 2CH3OH (VII) (CIF files CCDC 941186 (I), 1457906 (Ia), 1457905 (II), 941187 (III), 1457907 (IV), 1457908 (V), 1457909 (VI), and 941188 (VII)). The organic ligands in the complexes act as pentadentate neutral H2L or doubly protonated (H4L)2+ coordinated through the same set of donor atoms N3O2. In all compounds I–VII, the coordination polyhedron of the Co2+ ion in a complex with the Schiff bases has a shape of a pentagonal bipyramid. The hydrazones are arranged in the equatorial plane of the bipyramid. Its axial vertices are occupied by the nitrogen atoms of the NCS‾ anions in compounds I, II, and IV–VI and by the nitrogen atoms of NCS‾ and oxygen of the water molecule in compound III or methanol in compound VII. The NO 3 - anions or [Co(NCS)4]2‾ complex anions obtained by the reactions are involved along with the NCS‾ anions in the formation of compounds IV–VII.