Synthesis, structure characterization and Hirshfeld surface analysis of Ni(II) complexes with a flexidentate ligand: a dinuclear complex with O−H−O bond

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The ligand aminoethylethanolaminebenzoylacetone, H2L, reacts with nickel salts, both in the presence or in the absence of other salts such as KSCN and KCN. Mono- or di-nuclear complexes containing a monoanionic or doubly deprotonated ligand, depending on the reaction conditions, have been prepared. In complex 1, [Ni(HL)NCS], the H2L ligand acts as a N2O tridentate monoanionic ligand and the SCN anion coordinates to the nickel atom in a tetra-coordinated environment and exhibits a very slightly distorted square-planar geometry. The reaction of H2L ligand with Ni(ClO4)2 in the presence of KCN leads to the formation of complex 2, [(μ-H)(NiL)2]ClO4. In this reaction, potassium cyanide may act as a base to deprotonate the hydroxyl group of the ligand. The ligand acts as a N2O2 tetradentate ligand and two [NiL] units are tightly bonded together by a proton. The complexes have been thoroughly characterized by elemental analysis, FTIR and also by a single crystal X-ray diffraction study. In the reaction between NiSO4 and the H2L ligand, single crystal X-ray crystallography reveals that the H2L ligand, under these conditions, underwent hydrolysis, and complexes from the starting materials of the ligand synthesis were formed.