Igor S. Vasilchenko

Synthesis of cobalt(II), nickel(II) and copper(II) complexes with 2-(2-hydroxyphenyliminomethyl)-1-(4-methyl-phenylsulfonamido)benzene and crystal structures of {bis(methanol)[2-(2′-N-tosylaminophenyl)iminomethyl]phenolato}nickel(II) and {bis(2,2′-bipyridine)[2-(2′-N-tosylaminophenyl)iminomethyl]phenolato}copper(II)

Abstract Electrochemical oxidation of metal anodes (cobalt, copper and nickel) in acetonitrile solutions of 2-(2-hydroxyphenyliminomethyl)-1-(4-methyl-phenylsulfonamido)benzene (H2L) gave [CoL], [CuL] and [NiL] complexes. When 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) was added to the electrolytic cell, the mixed complexes [MLL′] (M=Co, Cu, L′=bipy or M=Ni, L′=phen) were obtained. A binuclear compound of composition [Ni2L2(MeOH)4] (1) was synthesized by reaction of the ligand H2L and nickel(II) acetate in methanol. X-ray structure determination showed the compound to be binuclear, with each nickel atom coordinated to two nitrogen and two bridging phenol oxygen atoms of two dianionic ligands and two methanol molecules, in an octahedral environment. The crystal structure of [CuLbipy] (2) was determined by X-ray diffraction; with the copper atom in a distorted bipyramidal environment defined by the two bipyridine nitrogen atoms and by the phenolic oxygen and the nitrogen atoms of the dianionic ligand. The electronic and vibrational spectral data of the complexes are discussed and related to the structure.

The novel azomethine ligands for binuclear copper(II) complexes with ferro- and antiferromagnetic properties

A series of novel binuclear ferro- and antiferromagnetic Cu(2+) chelates of structurally broadly varied Schiff bases (derived from o-tosylamino(hydroxyl)benzaldehydes and monoalkylated o-phenylenediamine, o-aminophenol, o-aminothiophenol, 1,2-diaminobenzimidazole, 1-aminobenzimidazoline-2-thione) and β-diketimines (derived from 2,6-di-i-Pr-aniline) has been prepared. The tautomerism of the ligands and structureof their copper complexes have been studied with the use of IR, 1H NMR EPR and EXAFS spectroscopy. Molecular and crystal structure of a β-diketimine copper dimer has been determined by X-ray crystallography. The magnetic measurements (2–300 K) performed for all the complexes showed that the ferro- and antiferromagnetic character of the exchange interaction depends both on the structure of the coordination site (origin of the ligating centers) and the structure of the ligands (in particular, on the type of the cycle annelated to the bridging fragment). Whereas S-binding metal chelates 13 (X = NTs, Y = S, R = H) are diamagnetic, the complexes 15 with annelated azole moieties are ferromagnetic.

Chapter 5 Hetarylazomethine Metal Complexes

Publisher Summary This chapter discusses hetarylazomethine metal complexe. This reactivity pattern is illustrated by the interaction of the aforementioned metal sources with cyclic and acyclic azomethines. Complexes of acyclic azomethines involve chelates of Schiff bases, b-aminovinylketones, and b-aminovinylimines containing heterocyclic moieties. In the multinuclear coordination compounds under this chapter, the heterocyclic frameworks play the role of the aldehyde, amine, and/or adduct-forming constituents. In the oligonuclear structures, heterocycles may also play the role of the intermetal bridges. The data collected in this chapter are generalized and systematized with emphasis on the specified functions in the structure of azomethine ligands and heterocyclic frameworks.

SOME ASPECTS OF COMPETITIVE COORDINATION OF β-DIKETONES AND NITROGEN-CONTAINING LIGANDS

Abstract Different coordination modes for transition metal atoms with typical chelating ligands such as β-diketones, o-oxyazomethines, azoles and azines are reviewed. Factors influencing the coordination such as ligand structure, methods and conditions of the synthesis, nature of solvent and specific hard-soft interactions are emphasized.

Review: Metal Complexes as Ligands

Ligand properties of coordination and organometallic compounds are examined on the basis of acid-base interactions of metal-containing bases and Lewis acids. Such interactions lead to homo- or heteronuclear di- and polynuclear complexes. Special attention is given to coordinatively-unsaturated molecules of classic Werner complexes, o -hydroxyazomethine chelates, metal carbonyls and their derivatives, ferrocenes with donor fragments, and coordinated heteroaromatic compounds.

Self-assembling tetranuclear complexes of a tridentate Schiff base

A tetranuclear KZn3 complex consisting of three tridentate dibasic N2O donor ligands (derived from mono-N-phenyl-substituted 5-nitro-o-phenylenediamine) and one methylato group has been synthesized. Single-crystal multi-temperature (100–350K) X-ray diffraction studies of the complex reveal that {[ZnL]3OMe}− units are assembled by K…ON2 contacts into layers. Mutual position of the KO6 and {[ZnL]3OMe}− fragments of neighboring layers is temperature dependent.

Direct electrochemical synthesis of novel transition metal chelates of tridentate azomethinic ligands

Abstract New chelates of the type ML(L 1 ) n ·MeOH ( n =1, 2) were obtained on the basis of the tridentate azomethinic ligands 2- N -tosylamine(2′-hydroxybenzal)aniline (L) and 2- N -tosylamine(2′-tosylaminobenzal)aniline (L 1 ) and zero-valent transition metals (Co, Ni, Cu, Zn, Cd) under electrosynthesis conditions. The mononuclear character of these products and the participation of N 2 O- or N 3 groups of the azomethinic ligands in the coordination are demonstrated by IR, 1 H NMR spectral and magnetic data (77–293 K).

Direct chemical and electrochemical syntheses of coordination compounds of benzazolyl azo ligands

The chelates of 2-hydroxy(aminophenylnaphthyl)-azo-1-alkylbenzimidazoles were obtained from electrochemical (anodic dissolution of zero-valent d-metals) and chemical (from acetates of the same metals) syntheses in methanol. The EXAFS and X-ray single crystal diffraction data revealed the existence of octahedral nickel, zinc, and cadmium complexes containing four five-membered metallocycles with the N4О2 or N6 ligand environments. The formation of five-membered coordination units, non-typical for azo ligands, is explained on the basis of inner-chelate competitive metal binding of ambidentate ligand systems.

X-ray diffraction, magnetochemical, and quantum chemical study of the structure and properties of binuclear copper(II) complexes

The binuclear chelates of copper(II) based on the tridentate azomethine ligands were synthesized and characterized by elemental analysis, IR, 1H NMR spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), and magnetic measurements. The quantum-chemical study of the structure and calculation of magnetic properties of the obtained metal-chelates was performed using the density functional theory with the broken symmetry technique. The performed magnetochemical studies in the temperature range 2–300 K suggest the existence of antiferromagnetic exchange interaction in all obtained complexes. The parameters of the exchange interaction −2J > 260 cm−1 were determined experimentally for all compounds, the experimental data is in a good agreement with the results of quantum-chemical calculations.

Trinuclear metal chelates of β-aminovinylimines

The chemical and electrochemical syntheses of Cu(II), Ni(II), Co(II), Zn(II), and Cd(II) trinuclear metal chelates with a new tetradentate ligand system including bis[(2-hydroxy-, -mercapto-, and -N-tosylamino)anils] of nitro- and phenylmalonaldehyde were performed. Temperature dependences of magnetic and ESR spectral properties of the complexes were studied to show that the antiferromagnetic spin-spin exchange interactions between copper(II) ions are intra- and intermolecular in nature and depend on the composition and structure of the coordination units, steric effects, nature of the substituent in the malonaldehyde moiety of the ligand, as well as on the method of synthesis of the complex compounds.