Research of nickel(II) complexes with aroyl hydrazones of 5,5-dimethyl-2,4-dioxogexane acid ethyl ester ergashov Mansur Yarashovich

Key words: benzoylhydrazone, ethyl ester of the 5,5-dimethil-2,4-dioxohexanoic acid, crystalline structure.

1. 
   INTRODUCTION
   

Recent years of research in the field of coordination chemistry are characterized by a steady trend towards a shift in the center of gravity from simple mononuclear compounds to more complex systems, which is primarily due to the search for new molecular materials and catalytic systems [1–3]. These works make it possible to draw substantiated conclusions and predict ways of targeted synthesis of complex compounds with desired properties [1, 3, 4]. We synthesized complex compounds [Ni(Ln) NH₃ n=1-6 and Ni(L⁶) 3Py] based on H₂L¹–H₂L⁶ [5, 6]. The resulting compounds are diamagnetic, soluble in chloroform, benzene, pyridine, and practically insoluble in water. The data of IR and 1H NMR spectra indicate a planar-square structure of the complexes.

2. 
   EXPERIMENTAL METHODOLOGY
   

We used the H₂L¹–H₂L⁶ ligands synthesized according to [8, 9], nickel(II) acetate, ammonia (all chemically pure), pridine (analytical grade), as well as the solvents EtOH, diethyl ether (“chemically pure”, distilled).
Synthesis of the NiL⁴.NH₃ complex. A hot solution of 1.25 g (0.005 mol) of Ni(II) acetate in 15 mL of concentrated ammonia and stirring has been continued for 30 minutes at 600C. A red solution has been obtained, from which red crystals precipitate after 5-10 minutes. The complex has been filtered off, washed with water and ethanol, and has dried in a vacuum desiccator over Р2О5. The yield of NiL⁴-NH₃ is 1.35 g (69%).
Other ammonia complexes Ni(II) and with the corresponding ligands H₂L¹–H₂L³ and H₂L⁵–H₂L⁶ have been synthesized similarly.
IR absorption spectra have been recorded on a Specord 75IR spectrometer in the range 400–4000 cm^–1 in KBr pellets.
The PMR spectra of 5-10% solutions of complex compounds have been recorded on a Bruker DPX-300 spectrometer (300.13 MHz).
Recrystallization of NiL⁶‧NH₃ from pyridine gave 2(NiC₃₂H₃₄N₆O₆) single crystals.
X-ray diffraction analysis of NiL₆‧3Py was carried out on an Xcalibur, Oxford Diffraction automatic diffractometer (CuK_-radiation, graphite monochromator, -scanning, 2_max=50^o. The structure has been solved and refined by least squares in the anisotropic approximation for non-hydrogen atoms. Hydrogen atoms have been localized from electron density maps of Fourier difference synthesis and refined in the isotropic approximation [5–7].

3.