Anodisation of copper in thiourea- and formamidine disulphide-containing acid solution.: Part I. Identification of products and reaction pathway

The anodic behaviour of copper in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea or formamidine disulphide was investigated at 298 K, combining data from electrochemical polarisation, chemical analysis, UV–vis spectroscopy, XPS and EDAX analysis, and structural information on copper–thiourea complexes. The main reactions depend on the applied potential and initial thiourea concentration. In the potential range −0.30≤E≤0.075 V (versus SCE), the electro-oxidation of thiourea to formamidine disulphide, the formation of Cu(I)–thiourea soluble complexes, and Cu(I)–thiourea complex polymer-like films, are the most relevant processes. The formation of this film depends on certain critical thiourea/copper ion molar concentration ratios at the reaction interface. At low positive potentials, the former reaction is under intermediate kinetic control, with the diffusion of thiourea from the solution playing a key role. For E≥0.075 V, soluble Cu(II) ions in the solution are formed and the anodic film is gradually changed to another one consisting of copper sulphide and residual copper. The new film assists the localised electrodissolution of copper. A complex reaction pathway for copper anodisation in these media for the low and high potential range is advanced.     

Studies on intermolecular interactions of metal chelate complexes. Part X. Interactions of metal chelates with ozone

Summary The interactions of more than forty metal chelate complexes, dithiocarbamates, dithiophosphates and acetylacetonates, with ozone are studied in homogeneous phase and the stoichiometry and the rate constants of the reactions estimated. Most powerful ozone deactivators are nickel(II) and copper(II) dithiocarbamate and dithiophosphate complexes interacting with 6.5 moles ozone per mole of the ligand with rate constant >0⁶m · I^–1 · s^–1. The remote ligand substituents do not influence the reaction parameters. Other sulphur-containing complexes of iron(III), cobalt(II), cobalt(III), zinc(II), manganese(III), bismuth(III), antimony(III), arsenic(III), cadmium(II), platinum(II), palladium(II) and chromium(III) deactivate 3–4 moles ozone per mole ligand with rate constants of 10²–10⁴ m · I^–1 · s^–1. Acetylacetonate complexes of copper(II), nickel(II), cobalt(III), iron(III), chromium (III), and oxovanadium(II) deactivate 1–3 moles ozone per mole ligand with a rate constant of 10–10⁴ m · I^–1 · s^–1. Using e.p.r. and electronic spectra, some intermediate products are detected and the mechanism of the reaction is discussed. The reported data are compared with other widely used antiozonants and the metal chelates are shown to have several advantages.     

Investigations of Cobalt, Nickel, and Copper Diethyldithiocarbamates Using Thermal Lens Spectrometry

Thermal lens spectrometry was used to study the dissociation kinetics of diethyldithiocarbamate complexes of copper(II), cobalt(III), and nickel(II) as a function of pH in the presence of chloride and sulfate ions. It is shown that, as distinct from conventional spectrophotometric and potentiometric measurements, the reversible dissociation of the test complexes and the irreversible oxidation of the ligand can be studied separately (at a level of n × 10^–8–n × 10^–6 M) using thermal lens spectrometry. Because of work in more dilute solutions and due account of the kinetic features of the systems in question, thermal lens spectrometry provides a higher accuracy of the determination of stability constants for diethyldithiocarbamate complexes of copper(II), cobalt(III), and nickel(II). The adsorption of the diethyldithiocarbamate complexes in question from water–ethanol solutions (1 : 3) on Silasorb C₁₈ silica is studied, and the adsorption constants are determined. The limits of detection of copper(II), cobalt(III), and nickel(II) diethyldithiocarbamates obtained in extraction–thermal-lens determination are n × 10^–8 M.     

Metal ion complexes of 2-picolinamineN-oxide

Summary A series of cobalt(II), nickel(II) and copper(II) complexes of 2-picolinamineN-oxide, HA, has been prepared. Solids of formula [M(HA)₃](BF₄)₂ (M=cobalt(II) or nickel(II); [Cu(HA)₂]X₂ (X=BF ₄ ^– , NO ₃ ^– ); [Co(HA)₂X₂] (X=Cl^– or Br^–); [Ni(HA)₂Cl₂] and [Cu(HA)X₂] (X=Cl^– or Br^–] have been isolated and characterized by partial elemental analyses, molar conductivities, magnetic susceptibilities, DSC-TGA, and spectral methods. All complexes were found to be monomeric, and their spectral parameters are compared with those of the metal ion complexes ofN-alkyl-2-picolinamineN-oxides, 2-dialkylaminopyridineN-oxides and 2-picolinamine. The cobalt(II) and nickel(II) halide complexes spectrally show a mixture of octahedral and tetrahedral centres.     

Chemistry of the phenylglyoxal-p-diethylaminoanil and/or thiourea substituted ammine complexes

Summary Mixed ligand complexes of chromium(III), cobalt(II), cobalt(III), copper(II) and zinc(II) involving either the phenylglyoxal-p-diethylaminoanil and/or thiourea, and ammonia have been obtained by the partial or complete replacement of the strongly coordinated ammonia of ammine complexes. All the products were characterized by elemental analysis, molar conductance, magnetic susceptibility and i.r. and electronic spectral measurements for their bonding and structures.     

Covalent immobilization of heparin on a collagen film

Four procedures for the covalent immobilization of heparin (Hp) on a collagen film (CF) have been investigated. In three of them (methods (I–A, B, C), the CF was first treated with epichlorohydrin and ammonia and the Hp was added with the aid of CMBC (method I–A), by reductive amination in the presence of NaCH CN (method I–B), and with the aid of CMEC after succinylation (method I–C). In the fourth procedure (method II), the CF was activated by treatment with alkali and the Hp was added with the aid of CMEC. It was shown that the maximum amount of Hp was immobilized by method II.M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 700–704, September–October, 1987.     

Electronic effects in dianion radicals of nitro derivatives of 2-phenylbenzimidazole

The EPR spectra of the dianion radicals of 5(6)-nitro-2-(4-aminophenyl)benzimidazole (I), 5(6)-nitro-2-phenylbenzimidazole (II), 5(6)-nitro-2-(4-nitrophenyl)benzimidazole (III), 5(6)-nitro-2-(3-nitrophenyl)benzimidazole (IV), and 2-(4-nitrophenyl) benzimidazole (V), obtained by electrochemical reduction in dimethylformamide (DMF) in a Bu₄NClO₄ -base electrolyte in the presence of Bu₄NOH (VI), were studied. Under the influence of VI, these compounds split out a proton from the imidazole ring and give anions I–V, which are capable of adding an electron reversibly. It was shown that the unpaired electron in I and II is localized in the benzimidazole system and that the splitting of the nitrogen atom of the nitro group does not depend significantly on the substituent in the phenyl ring. The introduction of a nitro group in the phenyl ring (III–V) leads to localization of the unpaired electron on it. The nature of the substituent in the benzimidazole system has a significant effect on the splitting constant for the nitrogen atom of the nitro group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 530–531, April, 1979.We thank T. A. Maslennikova for kindly providing us with the compounds for the investigation.     

Spectroscopic investigation of the cobalt(II), nickel(II), copper(II) and zinc(II) tetrahalometallates of theN-ethylmorpholinum cation

Summary Tetrahalometallates of the type (Etmorphl1)21MX4 (M = Co¹¹, Ni¹¹ or Zn¹¹ and with X = Cl, Br or l; M = Cu^II with X = CI or Br) and mixed tetrahalocuprates, Etmorphll)₂[CUX_mY_4–m] (X = Cl; N' = 13r; m = 1,2,3) of theN-ethylmorpholinium cation were prepared and investigated by means of spectroscopic and magnetic measurements. While the cobalt(II), nickel(II) and zinc(II) complexes appear to be essentially, tetrahedral, the copper(II) complexes are discussed on the basis of a distorted ('flattened') tetrahedral symmetry. The electronic spectra of the complexes are assigned on this basis. The far i.r. spectra of the complexes show bands which are unambiguously assignable to the metal-halogen stretching modes. The effects of the counter cation on the geometry around the metal ion, compared with that of the morpholinium and piperidinium cations, are discussed in relation to the pK_a of the amine.     

Copper(II), nickel(II) and cobalt(III) complexes of the macrocyclic ligand C-meso-7,14-diphenyl-5,6-butano-12,13-butano-1,4,8,11-tetraazacyclotetradeca-4,11-diene

Summary Metal complexes of the macrocyclic tetraaza ligand C-meso-7,14-diphenyl-5,6-butano-12,13-butano-1,4,8,11-tetraazacyclotetradeca-4,11-diene (L) are described. The copper(II) and nickel(II) complexes, isolated as their perchlorate salts, are 4-coordinate species. Several cobalt(III) complexes,trans-[CoLX₂]⁺(X = Cl^–, Br^–, NO ₂ ^– or N ₃ ^– have also been characterised. The most probable stereochemistry of the ligand in the metal complexes is the C-meso-N-meso arrangements of the chiral centres. The N-meso stereochemistry leads to the bulky phenyl groups lying in equatorial positions. I.r. and d-d spectra are reported for the various complexes described.     

Synthesis and characterization of cobalt(II), nickel(II), copper(II), palladium(II) and dioxouranium(VI) complexes of the antipyrine Schiff base of 3-formylsalicylic acid

A new Schiff base has been synthesized from 4-aminoantipyrine and 3-formylsalicylic acid. The ligand has a dianionic tetradentate compartmental OONO donor system. The cobalt(II), nickel(II), copper(II) and dioxouranium(VI) complexes exist in phenolato-bridged dinuclear species, while palladium(II) gives a mononuclear complex with free –COOH groups. The complexes have been characterized by elemental analyses, i.r., u.v.-vis, thermal and magnetic measurements.     

Synthesis and magnetism of tetrachlorophthalato-bridged cobalt(II) binuclear complexes

Three new cobalt(II) binuclear complexes have been prepared and characterized, namely [Co2(TCPHTA)(L)4](ClO4)2 [L=1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline(NO2-phen) and 2, 2-bipyridyl (bipy), respectively], where TCPHTA is the tetrachlorophthalate dianion. Based on i.r. spectra, elemental analyses and conductivity measurements, tetrachlorophthalato-bridged structures consisting of two cobalt(II) ions in which each cobalt(II) ion has a distorted octahedral environment are proposed for these complexes. The temperature dependence of the magnetic susceptibility for [Co2(TCPHTA)(L)4](ClO4)2·nH2O (L=phen, NO2-phen and bipy) has been measured over the 77–300 K range and the observed data successfully simulated by an equation based on the spin Hamiltonian operator (H=–2JS1S2), giving the exchange integral J=–2.92, –3.45, –4.03 cm–1, respectively. This result indicates the presence of a weak antiferromagnetic spin exchange interaction between the metal ions.     

Kinetics and Mechanism of Electroreduction of Ammonia Complexes of Cobalt(II) on a Dropping Mercury Electrode

Effects of concentrations of ammonia (0.3–5.8 M) and supporting electrolytes (NaF, NaClO₄; 0.1–0.5 M) on the kinetics of electroreduction of ammonia complexes of cobalt(II) at a dropping mercury electrode are studied. Most experiments are performed with low concentrations of cobalt(II) complexes (1 × 10^–5 to 2 × 10^–5 M) in the absence of a polarographic maximum. The dependence of the half-wave potential of the reversible cathodic wave pertaining to the reduction of ammonia complexes of cobalt(II) on the concentration of ammonia molecules is obtained. It is found from the dependence that, at ammonia concentrations of 0.5–2.6 M, the slow electrochemical stage involves predominantly complexes Co(NH₃)₂ ²⁺. At higher ammonia concentrations, the stage involves complexes Co(NH₃) _k ²⁺ (k > 2), which form in preceding chemical stages from complexes Co(NH₃) _i ²⁺ (i = 3–6) that are predominant in solution. Values of the diffusion coefficients for complexes Co(NH₃) _i ²⁺, apparent transfer coefficients, and rate constant of the process of electroreduction of ammonia complexes of cobalt(II) are determined. The reasons for the complicating effect the insoluble products of reduction of cobalt(II) complexes have on the shape of polarographic waves are discussed.     

The coordination chemistry of macrocyclic diamides. Transition metal complexes of 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane

Summary A convenient preparation of the 14-membered macrocyclic diamide 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane (LH₂) is described. The pK _NH ⁺ values of the ligand are pK₁ = 5.76 and pK₂ = 9.63 at 25° and I = 0.1 mol dm^–3 (KNO₃). With metal ions able to ionise amide hydrogens, the ligand acts as a planar quadridentate, L^2–. Thus copper(II) and nickel(II) give the neutral complexes ML, and conductivity measurements confirm that they are nonelectrolytes in aqueous solution. Both the nickel(II) and copper(II) complexes are acid labile unlike the analogues of 1,4,8,11-tetraazacyclotetradecane (cyclam).The cobalt(III) complex [CoL(NH₃)₂]Cl has been characterised and¹H n.m.r. measurements established the N-meso stereochemistry at the chiral nitrogen centres.     

Structural elucidation of o-vanillin isonicotinoyl hydrazone and its metal complexes

Summary A new series of complexes with the tridentate dibasic Schiff base ligand o-vanillin isonicotinoyl hydrazone (o-VINH) were prepared and characterized by i.r., ¹H n.m.r. and electronic spectral studies, magnetic susceptibility measurements and t.g.a. The disappearance of low field signals due to OH, NH protons at 10.23 and 9.31 p.p.m. and downfield shift of the –CH=N proton signal at 8.17 p.p.m. in the n.m.r. spectrum confirms the involvement of these groups in coordination. Both t.g.a. and i.r. spectral data show evidence for one molecule of coordinated H₂O. These results taken in conjunction with electronic spectral data allow assignation of tetrahedral geometry for manganese(II), nickel(II) and palladium(II) complexes but a square planar configuration to cobalt(II), copper(II) amd zinc(II) complexes.     

Complexation and Oxygenation in Cobalt(II)–Diamine–Oxygen Systems

The general pattern of equilibria involved in the complexation and oxygenation in cobalt(II)–diamine (phenanthroline or bipyridine)–oxygen systems was suggested. The set of equilibria included the following reactions: dissociation of protonated diamine cations; the formation of cobalt(II) mono-, bis-, and tris-diamine complexes, a hydroxo aqua complex, a hydroxo dimer, and a dihydroxo complex (monomer); various pathways to the dihydroxo dimer; and oxygenation of the hydroxo dimer. A mathematical model of the process was derived based on the material balances for cobalt and diamine and on the electroneutrality equation. The data of pH-metric studies of the systems in air and in an inert atmosphere and manometric data were used to calculate the individual equilibrium constants for each step of the process.     

Formation of cobaltic complexes by oxidation with potassium peroxymonosulfate in spectrophotometric determination of cobalt

Summary The oxidation of cobaltous complexes of amino-polycarboxylic acids to their corresponding cobaltic complexes with potassium peroxymonosulfate has been studied for simple spectrophotometric determination of 10–100 ppm of cobalt. The color reactions for cobalt are highly selective. Their molar absorptivities (200–300) and reduction potentials (about 0.45 v.) have been determined. The reactions are similar to that with hydrogen peroxide as an oxidant reported previously, but the peroxymonosulfate method has advantages over hydrogen peroxide because of no disturbance of gas bubbles, better stable color reactions, and elimination of ferric ion interference. The use of peroxymonosulfate as an oxidant for cobalt complexes of other ligands is also discussed.

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Herstellung von Kobalt(III)-Komplexen durch Oxydation mit Kaliumperoxymonosulfat zur spektrophotometrischen Bestimmung von Kobalt

Zusammenfassung Die Oxydation von Kobalt(II)komplexen der Aminopolycarbonsäuren mit Kaliumperoxymonosulfat wurde zwecks spektrophotometrischer Bestimmung von 10–100 ppm Kobalt untersucht. Die Farbreaktionen sind sehr selektiv. Ihre molare Extinktion (200–300) und ihr Reduktionspotential (etwa 0,45 V) wurden bestimmt. Gegenüber dem früher verwendeten Wasserstoffperoxid hat das Peroxymonosulfat den Vorteil, daß es keine Gasblasen bildet, daß die Farbreaktionen stabiler sind und daß Fe(III) nicht stört. Seine Verwendung auch für andere Kobaltkomplexe wurde diskutiert.

     

Five-coordinate Cobalt(II), Nickel(II) and Zinc(II) Complexes Derived from 2-pyridine-2-yl-3-(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one. The Crystal Structure of the Cobalt(II) Complex

The synthesis of cobalt(II), nickel(II) and zinc(II) complexes of 2-pyridine-2-yl-3(pyridine-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.–vis., i.r., 1D n.m.r., 2D hetcor and mass) and thermal studies. The cobalt(II) complex crystallizes as pink crystals in the monoclinic crystal system, space group P21/n with a = 10.066(6) Å, b = 15.929(9) Å, c = 12.624(7) Å, α = 90.00(9)°, β = 110.850 (8)°, γ = 90.00, V = 1891.5 (18) ų and Z = 4. The geometry around the cobalt atom is distorted trigonal bipyramidal with τ = 0.83 [structural parameter, τ = (β − α)/60; where α and β are the two basal angles in a five coordinate complex].     

Synthesis and Spectral Investigation of Some Transition Metal Complexes Containing Pentadentate Macroacyclic <Emphasis Type="Italic">NNNNN</Emphasis>-donor Schiff Base Ligands

A new Schiff base, 2,6-diacetylpyridine bis(2-hydrazinobenzothiazole) (DPHB), has been designed, and synthesized by the condensation of 2,6-diacetylpyridine with 2-hydrazinobenzothiazole, and structurally characterized. Copper(II), cobalt(II), nickel(II), manganese(II), zinc(II), cadmium(II) and oxovanadium(IV) complexes of DPHB have been synthesized for the first time. Their structures have been elucidated on the basis of elemental analyses, conductance measurements, magnetic properties, spectral (i.r., ¹H-n.m.r., u.v.–vis., e.p.r. and FAB-mass) and thermal studies. The complexes exhibit an octahedral geometry around the metal centre. The conductance data of all the complexes suggest them to be 1:1 electrolytes. The X-band e.p.r. spectra of the copper(II) and oxovanadium(IV) complexes in the polycrystalline state at room (300 K) and liquid nitrogen temperature (77 K) were recorded and their salient features are reported. Thermal stabilities of the manganese(II) and zinc(II) complexes have been studied.     

Interaction of Methyl Cysteine and Nitrilotriacetate with Transition Metal Ions

In the present work, sulfur-containing amino acid methyl cysteine was studied from the point of view of their coordinating ability with two metal ions, viz. copper(II) and cobalt(II). Solution equilibria of binary (Cu(II)/Co(II)–methyl cysteine and Cu(II)/Co(II)–nitrilotriacetate (NTA)) complex systems are investigated by paper ionophoresis at 35°C, ionic strength I= 0.1 mol/l. In addition to binary complexes, ternary complexes involving nitrilotriacetate and methyl cysteine were also studied. For studying mixed-ligand complexes, the pH of background electrolyte is brought to 8.5 (this pH value is purposely chosen because amino acid and NTA form very stable complexes much ahead of this pH). The stability constants of complexes (Cu(II)–NTA–methyl cysteine and Co(II)–NTA–methyl cysteine) were found to be 4.48 ± 0.07 and 3.55 ± 0.04 (logKvalues), respectively.     

Ligational behaviour of biacetylmonoxime-o-aminobenzoylhydrazone (H2BMAB) towards some dipositive metal ions

Summary Several new dipositive metal complexes with the hydrazoneoxime, derived from biacetylmonoxime ando-aminobenzoylhydrazine, have been synthesized and their structures elucidated by elemental analyses, conductivities, spectra (visible, i.r. and n.m.r.), magnetic and molecular weight measurements. The i.r. spectra show that the ligand, (H₂BMAB), behaves in a bidentate and tridentate manner. The stereochemistry of the cobalt(II), nickel(II) and copper(II) complexes is discussed. The cobalt(III) complex, [Co(BMAB)OH]_n, has also been isolated and characterized by conventional physical and chemical measurements and on the basis of molecular weight determination is probably a polymer, whereas the remaining complexes are monomers. I.r. and n.m.r. data suggest that the cobalt(III) complex contains hydroxo-bridge linking.