Voltammetric Determination of Cobalt(II) in Zinc Sulfate Solution

A method for automated polarographic analysis for Co(II) ions in technological solutions of zinc production was developed. The influence exerted by the components of a supporting electrolyte on the sensitivity and selectivity of measurements was studied. The method is intended for determining the content of cobalt(II) in purification of a zinc sulfate solution to remove impurities and for ecological monitoring of wastewater produced at nonferrous metallurgy plants.     

Ion Association and Hydration in Aqueous Solutions of Nickel(II) and Cobalt(II) Sulfate

Aqueous solutions of nickel(II) and cobalt(II) sulfate have been investigated at 25 ^∘C by dielectric relaxation spectroscopy (DRS) over a wide range of frequencies (0.2 ≤ ν (GHz) ≤ 89) and salt concentrations (0.025 ≤ c(mol-L⁻¹) ≤ 1.4). The spectra indicate, as for MgSO₄(aq) studied previously, the simultaneous presence of double solvent-separated, solvent-shared and contact ion pairs in both NiSO₄(aq) and CoSO₄(aq). The stepwise formation constants for each ion-pair type and the overall association constant, obtained from the data are in good agreement with ultrasonic relaxation and other estimates. The DR spectra at higher concentrations (c ≥ 0.5 mol-L⁻¹) suggest the existence of a nonlinear triple ion M₂SO₄²⁺(aq). Consistent with the very strong hydration of the salts, which have ‘effective’ hydration numbers approaching 27 at infinite dilution, there are no significant differences in any of the relaxation or thermodynamic parameters for NiSO₄(aq) and CoSO₄(aq), except that the triple ion appears to be somewhat more stable for the latter.     

Cobalt(II) complexes with hydantoin

Complexes of Co(II) with hydantoin (L, C₃H₄N₂O₂) have been synthesized. The complexes had the following compositions: [CoL₂(OH₂)₂](NO₃)₂ · 2H₂O, [CoL₂(OH₂)₂]Cl₂ · 3H₂O, and [CoL₂(OH₂)₂]SO₄ · 2H₂O. The individual character of the synthesized compounds are proved by the study of the IR absorption spectra (400–4000 cm^?1) of all the compounds and the initial ligand, as well as the X-ray diffraction patterns, thermograms, and thermogravigrams of the synthesized compounds. The coordination modes of the ligand and acido groups are revealed. The properties of the synthesized compounds are characterized.     

Strong Antiferromagnetic Exchange Interactions in Cobalt(II) Complexes with 2-Pyridyl Substituted Nitronyl Nitroxide Ligand

Three new complexes, [Co(hfac)₂(NIToPy)] (1), [CoCl₂(NIToPy)₂] (2), and [Co(NIToPy)₃](ClO₄)₂ (3), with NIToPy = 2-(2-Pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-oxy-3-oxide, and hfac = hexafluoroacetylacetonate, have been synthesized. The compound 3 crystallized in the monoclinic space group P2₁, with two molecules in a unit cell of dimensions a = 10.565(4) Å, b = 14.714(9) Å, c = 14.596(7) Å, and β = 107.10(4)°. The temperature-dependent magnetic susceptibility measurements (4.2 K-300 K) for the complexes demonstrated strong antiferromagnetic exchange interaction between cobalt(II) ion and NIToPy radical spins with J = ?140.1 cm^?1 for 1, J = ?94.2 cm^?1 for 2, and J = ?161.8 cm^?1 for 3, respectively. The magneto-structural correlation in these complexes has been discussed.     

Synthesis and Spin State of the Cobalt(II) Complexes with Substituted 2,6-Bis(pyrazol-3-yl)pyridine Ligands

Russian Journal of Coordination Chemistry - The direct template reactions afford the cobalt(II) complexes (I–III) with the hydroxy- and acetyl-substituted 2,6-bis(pyrazol-3-yl)pyridine...     

Complexes of Cobalt(II) and Zinc(II) with Heterocyclic Compounds Derived from 1,3-Indanedione

Complexes of Co(II) and Zn(II) with three-membered structures containing 1,3-indanedione, 1,3,4-thiadiazole, and pyridine moieties were obtained.     

Cobalt(II) halide complexes with ethyleneselenourea

The complexes obtained from ethyleneselenourea and cobalt(II) halides have been prepared and characterized. They have formula CoL₂X₂ (X = Cl, Br, I), tetrahedral stereochemistry and they are Se-bonded to the cobalt(II). They are comparatively studied with the previously reported complexes of cobalt(II) with ethylenethiourea, by IR and visible spectroscopy and magnetic susceptibilities. Using the average linand field approximation, the ethyleneselenourea is located at the very low end of the nephelauxetic series.     

The Liquid-Liquid Extraction of Copper(II), Nickel(II), and Cobalt(II) with 2,2′-Pyridil-mono-(2-quinolylhydrazone)

A 1:1 synthesis of 2-quinolylhydrazine with 2,2′-pyridil yields the hydrazone 2,2′-pyridil-mono-(2-quinolylhydrazone). In either the Z or E isomeric configuration, the molecule can serve as a tridentate ligand. Equilibrium studies were carried out to determine the effects of pH and concentration of ligand and metal on the distribution of the extracted complex into methyl isobutyl ketone. Graphical analysis of the slopes of the plot of the logarithm of the distribution coefficient vs pH, log [ligand], and log [M(II)] will determine the stoichiometry and polymerization of the complex. In the extraction of Cu(II), Ni(II), and Co(II), there is a small change in log D, where D is the distribution coefficient, with pH indicating the presence of a weakly dissociated ligand. Ligand:metal (1:1) ion-paired species are extracted, each having three absorption peaks in the region 400-550 nm. While a spectrophotometrtc method for each element does not seem feasible due to simultaneous extraction and overlapping absorbances, an extractive-atomic absorption method for the analysis of 1.6 ppm of Cu(II) is presented. Excesses of 20-70 ppm Co(II), Zn(II), Cd(II), Cl⁻, NO₃⁻, and SO₄²⁻ do not interfere.     

Fluorimetric Determination of Thiamine with Cobalt(II)

Abstract

A rapid fluorimetric method is reported for the determination of thiamine based upon its interaction with Co(II) ion in the presence of base and a nonionic Triton X-100 micellar medium. The effect of different experimental variables upon the fluorescence intensity were assessed. The detection limit for thiamine is 5.0 × 10^?8M (λ_ex =375nm, λ_em =433nm). The method was successfully applied for determination of thiamine in variety of samples with good accuracy being achieved.     

Studies on Cobalt(III) Metallosurfactants. Kinetics and Mechanism of Reduction of Cobalt(III) by Iron(II) in Aqueous Acid Medium

The kinetics and mechanism of reduction of the surfactant complex ions, cis-chloro/bromo(dodecylamine)(triethylenetetramine)cobalt(III) by iron(II) in aqueous solution were studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The second-order rate constant increases with cobalt(III) concentration and the presence of aggregation of the complex itself alters the reaction rate. The reductions are acid-independent in the range [H⁺] = 0.05–0.25 mol dm⁻³. Variation of ionic strength (μ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺(aq) with the cobalt(III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependent CMC and the standard Gibbs energy of micellization (ΔG_m⁰).     

Polynuclear Nickel(II) and Cobalt(II) Complexonates with Nitrilotrimethylenephosphonic Acid

Complexation in the Co(II)–H₆X–H₂O, Ni(II)–H₆X–H₂O, and Co(II)–Ni(II)–H₆X–H₂O systems (H₆X is nitrilotrimethylenephosphonic acid) was studied by spectrophotometry. The formation of binuclear complexonates Ni₂H₂X · 7H₂O, Co₂H₂X · 5H₂O, and NiCoH₂X · 6H₂O was demonstrated. These compounds were isolated from the solution, their composition was determined, the thermal stability was studied, and the kinetic parameters of dehydration were calculated.     

Cobalt(II) ion-selective electrode with solid contact

A new all plastic sensor for Co²⁺ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10⁻⁶ mol L⁻¹ and almost theoretical Nernstian slope in the activity range 4.0 × 10⁻⁶–1 × 10⁻¹ mol L⁻¹ of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co²⁺ in real samples and as an indicator electrode in potentiometric titration of Co²⁺ ions with EDTA.      

Cobalt(II) complexes ofSchiff bases derived from o-anisidine

A few complexes of cobalt(II) with monovalent tridentateSchiff bases have been prepared and characterised by elemental analysis. The magnetic, electronic and infrared spectral data show that cobalt(II) has coordination number six in these complexes.     

Open-Framework Cobalt (II) Phosphates with Sodalite-Related Architectures

Three new framework cobalt (II) phosphates have been synthesized hydrothermally in the presence of piperazine as a structure-directing agent. Crystal data: compound I, [C₄N₂H₁₂][Co(HPO₄)₂], monoclinic space group=P2₁/n 001(no. 14), a=8.5521(10) Å, b=13.5791(15) Å, c=10.0405(11) Å, β=96.855(2)°, V=1157.7(2) ų, Z=4, M=339.04, D_c= 1.945 g m−3, MoKα, λ=0.71073 Å, R₁(F₀)=0.053; compound II, [C₄N₂H₁₁][Co₂(PO₄)(H₂PO₄)₂], monoclinic space group=C2/c (no. 15), a=13.444(5) Å, b=12.874(5) Å, c=8.224(2) Å, β=94.64(2)°, V=1418.8 (2)A 3, Z=8, M=494.96, D_c=2.317 g cm−3, MoKα, λ=0.71073 Å ,R₁(F₀)=0.047; compound III, [C₄N₂H₁₂]₂[Co₄(HPO₄)₆], monoclinic space group=P2₁/c (no. 14) a=12.8780(13) Å, b=26.671(3) Å, c=8.2592(8) Å, β=96.931(2)°, V=2816.0(5) Å3, Z=4, M=987.90, D_c=2.330gcm-3, MoKα, λ=0.71073 Å, R₁(F₀)=0.048. The structure of I consists of one-dimensional chains built up of corner-shared four rings (Co₂P₂) which are key structural units that form the sodalite cage. Compounds II and III have interrupted sodalite-type structures resulting from the removal of Co²⁺ atoms from sites related by two-fold axes passing through the four rings of the normal sodalite cage structure. The modes of the interruptions in II and III differ in relation to the structure of a regular sodalite cage.     

Cobalt(II), nickel(II) and zinc(II) coordination compounds derived from aromatic amines

The structural and spectroscopic characterization of coordination compounds of four aromatic amines derived from benzimidazole, 2-aminobenzimidazole (L1), 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2), 2-(2-aminophenyl)-1H-benzimidazole (L3) and 6,6-dimethyl-5H-benzimidazolyl[1,2-c]quinazoline (L4) are reported. Cobalt(II) [Co(L1)₂(CH₃COO)₂] (1) and nickel(II) [Ni(L1)₂(CH₃COO)₂] (2) acetate coordination compounds of L1 are discussed. The synthesis and the X-ray crystal structure of the new 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2) is informed, together with its cobalt(II) [Co(L2)₂Cl₂] (3), [Co(L2)₂Br₂] (4) and zinc(II) [Co(L2)₂Cl₂] (5), [Zn(L2)₂Br₂] (6) coordination compounds. In these compounds the imidazolic nitrogen is coordinated to the metal center, while the ArNH₂ and the S-methylcarbodithioate groups do not participate as coordination sites. A co-crystal of L1 and L2 is analyzed. Structural analyses of the coordination compounds of L3 showed that this ligand behaves as a bidentate ligand through the aniline and the imidazole groups forming six membered rings in the cobalt(II) [Co(L3)Cl₂] (7) and zinc(II) [Zn(L3)Cl₂] (8) compounds, as well as the nickel(II) nitrate [Ni(L3)₂(H₂O)₂](NO₃)₂ (9). The quinazoline L4 was produced by insertion of one acetone molecule and water elimination in L3, its X-ray crystal diffraction analysis, as well as that of its zinc(II) coordination compound [Zn(L4)₂Cl₂] (10), are discussed.     

Cobalt(II) complexes of creatinine

Summary Cobalt(II) complexes of creatinine [Co(creat)₂X₂] (X = Cl, Br, I or NCS) and [Co(creat)₂X₂(H₂O)₂] (X = HCO₂, HOCH₂CO₂ or CNCH₂CO₂) have been prepared. Their i.r. spectra show an increase in (NH) of the cyclic secondary amine group, compared to free ligand (3300 cm^–1), indicating that cyclic nitrogen is involved in coordination. The thiocyanate group coordinates through nitrogen and carboxylates coordinate as univalent unidentate ligands. The electronic spectra and magnetic moments suggest a d⁷ configuration for cobalt: a tetrahedral geometry (4.4 B.M.) for halide and thiocyanate complexes, and an octahedral geometry (5.0 B.M.) for the carboxylate complexes. On heating, the ligand moiety is lost and the respective cobalt halide or cobalt carboxylate is formed, which is converted finally into Co₃O₄. There is a correlation between the high intensity electronic transitions and the polarographic half-wave potentials.     

Cobalt(II), nickel(II) and copper(II) with 2-substituted benzimidazole complexes

Summary Complexes of stoichiometries M(Acbim)₂X₂·nH₂O and M(Bzbim)₂X₂·nH₂O (M = Co, Ni or Cu; Acbim = 2-acetylbenzimidazole, Bzbim = 2-benzoylbenzimidazole; X = Cl, Br, NO₃ or ClO₄; n = 0, 1 or 2) have been prepared and characterised by spectroscopic and physicochemical methods. The ligands coordinate through carbonyl oxygen and tertiary nitrogen.     

Complexes of Cobalt(II), Nickel(II) and Copper(II) Chloroacetates with Quinoline N-Oxide

Some 1:1 and 1:2 adducts of cobalt(II), nickel(II) and copper(II) chloroacetates with quinoline N -oxide have been isolated by the interaction of the appropriate metal chloroacetate with quinoline N -oxide (QuinNo). The complexes isolated are of 1:1 stoichiometry of formula [M(CH₃_xClxCOO)₂QuinNO] (when M=Co(II), Ni(II); X=1,2 and 3 and when M=Cu(II), X=l and 2) except copper(II) trichloroacetate which yields an adduct of 1:2 stoichiometry of formula[Cu(CCI₃COO)₂(QuinNO)₂]. The adducts isolated are soluble in common organic solvents.     

Cobalt(II), Nickel(II), and Copper(II) Complexes with Diphenylthiocarbazide

New [ML(H₂O)₂] complexes (M = Co²⁺, Ni²⁺, or Cu²⁺; H₂L = diphenylthiocarbazide) were synthesized and studied using IR and diffuse reflection electronic spectroscopy, magnetic chemistry, conductometry, and DTA. The metals were shown to coordinate L^2–through nitrogen and sulfur atoms. The complex [CuL(H₂O)₂] is a dimer.