Binuclear complexes of silicon(IV) chloride with nickel(II) salicylaldoximates

Some binuclear complexes of silicon(IV) chloride and nickel(II) salicylaldoximates were synthesized and characterised by elemental analyses, conductivity measurements, magnetic and spectral data. The complexes were proved to be 1:1 SiCl₄ adducts. The resulting complexes were amorphous in nature and electrolytes in solution.     

Synthesis and spectral studies of copper(II) complexes with amide group ligands

Complexes of copper(II) with 2-(acetylamino)benzoic acid, 2-(benzoylamino) benzoic acid, 2-(aminocarbonyl)benzoic acid, 2-[(phenylamino)carbonyl]benzoic acid, 2-[(1-naphthalenylamino)carbonyl]benzoic acid, 2-[(2-aminophenylamino)carbonyl]benzoic acid, 2-aminobenzanilide, 2(aminobenzoyl)benzoic acid, maleanilic acid and malea-1-naphthalanilic acid have been prepared and characterized by chemical analyses, molar conductivity, magnetic susceptibility measurements, thermal data, IR, electronic and ESR spectra. The visible and ESR spectral studies of these complexes (except those of maleanilic acid and malea-1-naphthalanilic acid) indicate that they are monomeric having either square planar or distorted octahedral geometry around Cu(II). The Cu(II) complexes of maleanilic acid and malea-1-naphthalanilic acid have been tentatively assigned dimeric structures. From the ESR spectra of Cu(II) complexes various parameters have been calculated.     

Cyclic voltammetric studies of copper(II) dipeptide complexes. Evidence for copper(I) dipeptide complexes in aqueous media

The reduction of the title complexes was studied by cyclic voltammetry in aqueous media. It proceeds through a one-electron process generating intermediate copper(I) dipeptide complexes. The copper(I) dipeptide complexes are found to be short-lived and undergo transformations eventually generating Cu⁰ at the mercury electrode. The unchanged fraction of the copper(I) species is re-oxidised to the copper(II) complexes. The Cu⁰ generated undergoes a two-electron oxidation at a more anodic potential than the copper(I) complexes. pH-dependence of the title complexes is also investigated by cyclic voltammetry.     

Four- and five-coordinate copper(II) complexes containing mixed ligands

New copper(II) complexes of general formula, Cu(ONS)B (ONS = the di-negatively charged Schiff base, S-benzyl-β-N-(2-hydroxyphenyl) methylendithiocarbazate; B = pyridine, 2,2′-dipyridyl or 1,10-phenanthroline) have been synthesized and characterised by magnetic and spectroscopic measurements. The complex, Cu(ONS)py is four-coordinate and square-planar. Magnetic and spectroscopic data support a five-coordinate, presumably, a trigonal-bipyramidal structure for the [Cu(ONS)dipy] and (Cu(ONS)phen] complexes     

Spectroscopic studies on copper(II)triphenylarsine oxide square planar complexes

Electronic and ESR spectra of the complexes [Cu(II)(tpa_so)₄][Cu(I)Cl₂]₂,[Cu(tpa_so)₄](NO₃)₂ and [Cu(tpa_so)₄](ClO     

Tetragonal distortions and vibronic coupling in hexaflouro nickel(II) and copper (II) complexes

Two parameters, axial (R_a) and equatorial (R_e) metal-ligand distances, describe the tetragonal distortions of the NiF^4?₆ and CuF^4?₆ complexes under study. The experimental values of R_a plotted vs R_e exhibit a smooth curve type dependence valid for MF₆ chromophore of solid state compounds. In the model study it becomes explained by analyzing the shape of the adiabatic potential surface (APS) of the form of E_T(R_a, R_e). Around the energy minima the map of numerical values (obtained by the quantum-chemical CNDOUHF and INDOUHF methods) was transformed to an analytic form from which the quantitative characteristics of APS were obtained in a new, simple way. The set of equatorial-axial parameters as well as the set of vibronic parameters were evaluated and discussed in more detail.     

Cyclic voltammetric studies of copper(II) amino acid complexes: electrochemical evidence for the generation of copper(I) complex as an intermediate

The reduction of the title complexes is studied by cyclic voltammetry in aqueous media. It proceeds through a one-electron process generating the corresponding copper(I) amino acid complexes. The reduced copper(I) species undergo chemical reactions generating Cu(O) at the mercury electrode. The unreacted fraction of the copper(I) species is re-oxidised to the copper(II) complexes. The Cu(O) generated undergo a two-electron oxidation to Cu²⁺ at less cathodic potentials which get reduced to Cu(O) subsequently. pH-dependence of these complexes is also investigated.     

Mixed ligand complexes involved in the system pyridoxamine-glycylglycine-imidazole copper(II)

Ternary as well as quaternary complexes involved in the system pyridoxamine-glycylglycine-imidazole-copper(II) have been studied by pH-metric titration at 37°C and I = 0.15 M (NaNO₃). The data were assessed by program MINIQUAD 75. The formation constants were compared with those obtained from the system of pyridoxamine-glycine-imidazole with some bivalent metal ions previously reported. They are ～ 2.5 log units less. In addition, the enhancement of quaternary complex formation has been described in terms of binary and ternary complex formation reactions. It has been also found that deprotonation of the peptidic proton of glycylglycine took place in the presence of more than one different ligand.     

Preparation and characterization of copper(II) and nickel(II) complexes with novel tetraaza-macrocyclic schiff bases

Novel tetraaza-macrocycles with N-substituted carbamoyl groups were prepared by the reaction of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,12-tetraene with isocyanates (RNCO, R = Ch₃ and C₆H₅). Their copper(II) and nickel(II) complexes were characterized by magnetic susceptibilities, electronic absorption spectra, and electrochemical properties. The complexing abilities and extractabilities of the ligands for the metal ions were investigated.     

Extraction of copper(II) and nickel(II) by nopinoquinone dioxime

In the research for a selective extractant for nickel a strained dioxime, β-nopinoquinone dioxime, has been studied in its extraction properties for copper(II) and nickel(II). Spectroscopic investigations (ESR and NMR) showed that both copper and nickel are extracted as a N,N-coordinated chelate. The extraction studies showed that the use of strained instead of aliphatic dioximes makes the extraction more convenient because of the higher extraction rate, but the selectivity for nickel above copper disappears.δ-nopinoquinone dioxime is easily converted into its furazan by treatment with 1N NaOH. This furazan is a rather weak ligand without significant extraction capacities.     

Extraction of copper(II) and nickel(II) by long-chain aliphatic dioximes

In the search for a selective nickel extractant symmetric dialkyl dioximes have been studied in the extraction of copper and nickel ions from ammoniaca     

Formation equilibria of copper(II) complexes with some pyridinols in various solvents

Complexation of copper(II) with two different pyridinols in three solvents has been studied by visible spectrophotometry and flow-microcalorimetry. The influence of the solvent on tautomeric equilibrium of the ligand, on distribution, on stability and on formation enthalpies of the main complex species is discussed.     

Manganese(II) and copper(II) complexes of some nitrogenoxygen and nitrogensulphur donor ligands

Manganese(II) and copper(II) complexes of the type M(ligandH)₂ with some nitrogenoxygen and nitrogensulphur donor ligands (HL) viz. phenylpyruvic acid semicarbazone (ppysc), 4-methylphenylpyruvic acid semicarbazone (4-mppysc), phenylpyruvic acid thiosemicarbazone (ppytsc) and 4-methylphenyl pyruvic acid thiosemicarbazone (4-ppytsc), have been synthesised. All the complexes have been characterised by magnetic moment measurements, IR electronic and electron spin resonance special studies. All the ligands behave as tridentate.     

Copper(II) and nickel(II) complexes of a neutral pentadentate Schiff base

A new pentadentate Schiff base 2,6,10-triaza-1,11-bis(2′-aminophenyl)-undeca-1,10-diene, abaDPT, and its complexes of general formula M(abaDPT)X₂ where M = Cu(II), Ni(II), X = Cl, Br, I, NO₃ and ClO₄, have been prepared. The complexes have been characterized by electronic and IR spectra, EPR, magnetic moments, molar conductances, and elemental analysis. IR data show an interaction between halide anion of the outer coordination sphere and the complexed amino group. EPR and spectrophotometric data of most of the copper compounds are consistent with a distorted square pyramidal geometry. Single crystal EPR studies of Cu(abaDPT)(NO₃)₂ and Cu(abaDPT)Br₂ revealed that copper atoms in the former compound occupy two magnetically inequivalent places in the lattice while copper atoms in the latter compound take identical sites. Principal g tensor axes of the two compounds have been determined.     

Dinitrogen complexes of iron(II) with chelating agents as ligands

Two new dinitrogen compounds of formulae Na₂[Fe(EDTA)N₂].2H₂O and Na₂[Fe(CDTA)N₂].2H₂O have been synthesized from [Fe(H-EDTA)H₂O] and [Fe(H-CDTA)-H₂O], respectively, and NaN₃. Both complexes have been characterized by IR and electronic spectra. The thermal behaviour has been studied by TG and DTA techniques.     

Structure of a diruthenium(II,III) complex with benzamidato bridging ligands

The compound Ru₂Cl(C₆H₅CONH)₄ has now been obtained in crystalline form and the crystal and molecular structure determined by X-ray met     

Synthesis and spectroscopic studies of dimeric copper(II) complexes containing imidazoles and dipeptides

Six dimeric copper(II) complexes of the type Na[Cu₂(D)(L)], where D = glycylglycinate dianion, and HL = imidazole and 2-methylimidazole; D = glycyl-L-tyrosinate dianion, HL = imidazole and benzimidazole; D = glycyl-L-phenylalaninate dianion, and HL = imidazole; and D = glycyl-L-tryptophenate dianion, and HL = benzimidazole, have been prepared. They were characterized by IR, visible absorption, and EPR spectroscopy. The EPR data indicated their complete dimeric behaviour in basic solution with two Cu(II) ions in close proximity of <7Å with imidazolate, 2-methyl-imidazolate, and benzimidazolate bridges.     

Magnetic and electronic characterization of 2:1 copper(II) complexes of a series of aminocarboxylic acids

Copper(II) complexes with L-(—)-proline, pipecolinic acid, picolinic acid, anthranilic acid, 4-chloranthranilic acid, 3,5,-dichloroanthranilic acid, 4-nitroanthranilic acid, N-phenyl-anthranilic acid, and flufenamic acid anions were prepared and characterized. The copper complexes of the anions of proline, pipecolinic acid, and picolinic acid are soluble in polar solvents and display frozen solution EPR spectra with axial resonance parameters. The copper complexes of the ring-substituted anthranilates are highly insoluble or only slightly soluble in a few solvents. The EPR spectra of the copper-doped zinc(II) analogues of these complexes display various degrees of rhombicity in their EPR parameters. The N-substituted anthranilates form insoluble complexes in aqueous solution which readily dissolve in organic solvents and undergo dimerization.     

Catalytic activity of binuclear planar copper(II) complexes for the decomposition of hydrogen peroxide

Planar binuclear copper(II) complexes generally showed high catalytic activities for the decomposition of hydrogen peroxide compared with the relevant planar mononuclear copper(II) complexes. This result was explained on the assumption that the two-electron transfer occurs between H₂O₂ molecules via an intervening binuclear copper(II) complex.     

Cyanato-copper(II) complexes with organic ligands—XXIV. Diisocyanato-bis(3,5-dimethylpyrazole)copper(II)—the cyanate member of the coligand isomer

The title compound was prepared, and found to be isomeric with the known bis(1-carbamoyl-3,5-dimethylpyrazolato)copper(II). Its IR, far-IR, electronic