Synthesis, Spectroscopic Properties of Nickel (II) Complex of the New Bis Amide Ligand N, N'- Alkanelid Bis Amide [Ni(NABA)]⁺

Bis amides have often been used as chelating ligands in the field of coordination chemistry and their metal complexes are of great interest for many years. It is well known that N atom plays a key role in the coordination of metals at the active sites of numerous metallobio molecules.¹ Bis amides metal complexes have been widely studied because they have industrial, antifungal, antibacterial, anticancer and herbicidal applications.^2-3 They serve as models for biologically important species and find applications in biomimetic catalytic reactions. Chelating ligands containing N, S and O donor atoms show broad biological activity and are of special interest because of the variety of ways in which they are bonded to metal ions. It is known that the existence of metal ions bonded to biologically active compounds may enhance their activities.^4-6 The variety of possible bis amides metal complexes with wide choice of ligands, and coordination environments, has prompted us to undertake research in this area.⁷ Nickel can function as active site of hydrolytic enzymes, where it is ligated by hard donors (N or O). It has long been recognized as an important co-factor in biological molecules, either as a structural template in protein folding or as a Lewis acid catalyst that can readily adopt the coordination numbers 4, 5, or 6.^8-10 The catalytic role of Ni comprises Lewis acid activation of substrate, generation of a reactive nucleophile and stabilization of the leaving group. As a part of our continuing work on dissymmetric tetradentate bis amides complexes containing N, S and O donor atoms¹¹ and in light of the importance of Ni ion metal, recently, there has been a considerable interest in the chemistry of bis amides compounds because of their potential pharmacological applications. Several reports on synthesis of metal complexes of bis amide by the use of organic solvents under reflux and their biological properties have already been published. More so, these methods suffer several drawbacks such as long reaction time, an excess of organic solvent, lower products yield and harsh refluxing conditions. We now report the synthesis and characterization of Ni (II) complex of the N, N’- alkanelid bis amide ligand.

Experimental

Material And Method

All reagents were supplied by Merck and were used without further purification. Melting point was determined in an Electrothermal 9200. The FT- IR spectra were recorded in the range 400–4000 cm^-1 by KBr disk using a Bruker Tensor 27 M 420 FT-IR spectrophotometer. The UV–Vis spectra in CH₃CN were recorded with a WPA bio Wave S2 100 spectrophotometer. Elemental CHN analyses were performed using a Heraeus CHN-O-RAPID elemental analyzer.

Synthesis Of The NABA Ligand

For synthesis of the NABA ligand, to a magnetically stirred of acetamide (1.13 g, 10mmol) in CH₂Cl₂ (10 ml) and hydrochloride acid (10ml) was added 4-methylbenzaldehyde (0.53g, 5mmol) via a syringe and heated for 4 h. After cooling to room temperature, the resulting white precipitate was filtered, washed with n-hexane (20 ml) and dried. M.P.: 235-237º C Yield: 89%. Anal. Calc. for C₁₁H₁₄N₂O₂: C, 64.07; H, 6.79; N, 13.59%. Found: C,64.18; H, 6.95; N, 13.83%. IR (KBr Disk, cm^-1): 3279(w, N-H), 3111(w, C=O); 1381 (w, C=N); 690(s,C-H). (Figure1, 2, Table 1).

Figure 1: FTIR spectrum of NABA (KBr Disk)

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Figure 2: ¹H-NMRspectrum of NABA (in CDCl₃)

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Table 1: FTIR spectral data (cm^-1) of NABA

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Preparation Of [Ni(Naba)]+ Complex