Complexation of Cu(II) with Hetarylformazanes in Solutions, Polycrystals, and Modified Anionite

Abstract

The reactions of formazanes with transition metal ions can give coordination compounds of different nature and structures, namely, mono-and binuclear complexes, complexes with different surrounding of a central atom and configuration. The reason for such a variety lies in a high flexibility of formazanes, their capability to act as bi-, tri-, or tetradentate ligands with allowance for the substituents [1].Formazanes and their compounds are widely used in chemistry, in particular, as analytical reagents. The polymeric ionites modified with formazanes significantly improve the ionite selectivity toward the adsorbed metal ions [2].The goal of this work was to study the Cu(II) complexes with hetarylformazanes ( HF ) in solutions, modified AN-18 anionite, and in polycrystals. The following ligands were used in this work:The authors of [3][4][5] used the NMR and X-ray diffraction methods to study the Ni(II), Co(II), and Cd(II) complexes with hetarylformazanes containing substituents R 1 , R 2 , and R 3 that were different from those we used. They established that the complexes under study had octahedral structure (coordination number 6) with the N 1 and N 4 atoms of the formazane fragment and the N 6 atom of heterocycle participating in coordination with a metal.A significant broadening of lines in the NMR spectrum of the Cu(II) complexes due to the spin paramagnetism effect does not make it possible to use the NMR method in order to study the structure of the Cu(II) complexes with formazanes. Therefore, we used the Abstract -The Cu(II) complexes with hetarylformazanes (HF) formed in solutions, polycrystals, and AN-18 polymeric ionite modified with HF were studied by EPR method and were found to have almost identical structures. The configuration of the Cu 2+ coordination surrounding (square-planar or pseudotetrahedral) is specified by the substituents at N 1 in formazane fragments. Complexes with coordination unit Cu(4N) were formed mainly, when the ligands were taken in excess, while in the case of the ligand deficiency and with the coordinating OH group in benzene ring, the complexes with the Cu(3NO) coordination unit were formed. The covalence of in-plane metal-ligand σ -bond was found to be affected by the substituents. The formation of binuclear copper complexes in solutions and polycrystals was established in the case of deficiency of the ligand with SO 3 H substituent in benzene ring.

Formazans and their metal complexes

“…85 It was found that depending on the nature of the substituents at the N(1) atom, the copper atom acquires a squareplanar or a pseudo-tetrahedral configuration. For L 2 Cu complexes prepared in an excess of a ligand, the coordination unit CuN 4 formed contained the N(1) and N(5) atoms of formazan (see structure 37).…”

Synthesis and Catalytic Properties of Copper(II) 1-Aryl-5-Benzothiazolylformazanates

“…The ESR data show the square-planar structure of the coordination core Cu³4N³ for formazanate VIIIp and Cu³3N, O³ for VIIp, similarly to the initial complexes VIII and VII [8,9]. Presumably, immobilization of formazanates IV3VI on the polymeric support does not change the structure of the coordination core.…”

“…All the compounds are crystal solvates with ethanol. The electronic absorption spectra of complexes IV3VIII in ethanol are The ESR spectra of copper(II) formazanates in toluene [8] suggest formation of a Cu³4N³ distorted tetrahedron for V, Cu³4N³ square-planar structure for VIII, and mixed nitrogen3oxygen Cu³3N, O³ structure for VII.…”