- Mixed- ligand Complex Formation of Cobalt(II), Nickel(II) and Zinc(II) with N-Benzenesulphonyl-l-cysteine as Primary Ligand and Bipyridine, Ethylenediamine and Glycinate as Secondary Ligands
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Equilibrium study on the complex formation of M2+ ions (M = Co, Ni and Zn) with N-benzenesulphonyl-l-cysteine (NBSCH2) in the presence of bipyridine, ethylenediamine, glycinate (B) indicates the formation of mixed-ligand complexes of the types M(NBSC)(B), M(H-I NBSC)(B) and M(H-I NBSC)(OH), together with binary M(NBSC) and M(B) complexes. Formation constants of the complexes have been determined by potentiometric method at 25±0.1° in 50% (v/v) ethanol-water medium at a constant ionic strength, I=0.2 M (NaNO3). Stability of the complexes has been correlated with the modes of coordination of NBSC, basicity of the B ligands and π-electron delocalisation in the metal-ligands bonds.
- Mukherjee,Ghosh
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- Oxidation of Allyl Alcohol by Diperiodatonickelate(IV) in Aqueous Alkaline Medium
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The rate of oxidation of allyl alcohol (AA) by alkaline diperiodatonickelate(IV) (DPN) is found to decrease with increase in periodate concentration and increase with increasing OH- concentration.The reaction is first order in and fractional order in and ->.Based on the results a suitable mechanism is proposed.The rate law derived from this mechanism is verified and some reaction constants are also found.
- Tuwar, S. M.,Nandibewoor, S. T.,Raju, J. R.
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p. 651 - 653
(2007/10/02)
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- Kinetics and mechanism of dissociation of di-(2-pyridyl)amine complexes of copper (II), nickel (II) and cobalt (II) in aqueous acid media
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Kinetics of dissociation of ML2+2 (M=Cu(II), Ni(II) and CoL2+ complexes in acid media forming aqua-metal ions and the protonated ligand as the ultimate products have been studied by stopped-flow spectrophotometry.Dissociation of the bis-complexes occurs in two consecutive steps through formation of the mono complexes in the first step, which is faster than the second.For each of the steps of the different complexes the observed rate constant kx shows acid dependence.Arguments have been put forth in favour of chelate ring-opening as the rate-determining step.These complexes are much more labile to dissociation than the corresponding complexes of 2.2'-bipyridyl.
- Das, Asim K.,Banerjea, D.
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p. 347 - 349
(2007/10/02)
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- ETUDE DES COURANTS PERIODIQUES OBSERVES LORS DE LA DISSOLUTION ELECTROCHIMIQUE DU NICKEL EN PRESENCE D'IONS IODURE ET CHLORURE EN MILIEU AQUEUX
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Electrodissolution of nickel in the presence of chloride and iodide ions has been investigated using low sweep voltammetry (a delay shortened by increasing the iodide concentration.These oscillations occur over a wide range of potential provided the iodide concentration is kept low.Increasing this concentration suppresses the oscillations, while two peaks appear, the more cathodic becoming progressively larger.Addition of some surfactants is discussed and progressively larger.Addition of some surfactants is discussed and only SOBS (sodium p-octylbenzene sulfonate) suppresses the oscilations even at low concentration, while starch acts progressively from 1 to 40 g/L.Changes of color of the nickel surface during the oscillations suggests a preferential dissolution at the grain boundaries, explaining the black color observed alternatively with a metallic appearance, the nickel being at this time covered with finely divided particles that dissolve quickly.Iodide, appearing only occasionally at such anodic potentials, is probably involved in the dissolution process.
- Le, Li Ben,Vittori, Olivier
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p. 1525 - 1528
(2007/10/02)
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- Molten lithium sulfate-sodium sulfate-potassium sulfate eutectic: Reactions of some sulfur compounds
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The reactions of sulfide and of five sulfur oxyanion salts (Na2SO3, Na2S2O5, K2S2O5, Na2S2O3, and K2S2O7) were studied by themselves and in the molten ternary sulfate eutectic under nitrogen, with air, sulfur dioxide, sulfur trioxide, and carbon dioxide, and with acidic, basic, and reducing solutes. The sulfur-containing products were elemental sulfur and sulfate though sulfur oxides were sometimes evolved and a number of intermediates formed. Reaction products were identified qualitatively and quantitatively, often by TGA, and reaction schemes are suggested.
- Dearnaley,Kerridge,Rogers
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p. 3242 - 3247
(2008/10/08)
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- Substitution reactions of five-coordinate complexes. 2. Mechanism of ligand replacement in trigonal-bipyramidal nickel(II) and platinum(II) complexes containing the tetradentate ligand tris(o-(diphenylarsino)phenyl)arsine
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Ligand replacement of the monodentate ligand in a series of trigonal-bipyramidal nickel(II) complexes containing the tetradentate ligand tris(o-(diphenylarsino)phenyl)arsine, QAS, is reported for methanol solutions. Entering ligands replacing Br- in order of decreasing rate were SC(NH2)2 ? CN-, > N3- > SCN- > I- > NO2- ? PPh3. CN- replacement of leaving groups in order of decreasing rate were NCS- > N3- > Cl- > Br- > NO2- > I-. A second consecutive decomposition was observed to be several orders of magnitude slower than ligand replacement when CN- was the entering ligand. The kinetic data obtained at 0.050 M ionic strength and 25.0°C are consistent with either an associative interchange, Ia, mechanism or a mechanism involving formation of a four-coordinate intermediate via partial dissociation of the tetradentate ligand.
- Collier, Harvest L.,Grimley, Eugene
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p. 511 - 515
(2008/10/08)
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- Multidentate ligand kinetics. VIII. The effect of hydroxide, acetate, and azide complexes of copper(II) in its reaction with ethylenediaminetetraacetate complexes
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The kinetics of the reaction of copper(II) with the ethylenediaminetetraacetatozincate(II) and -nickelate(II) complexes are studied in the presence of various anions at 25.0° and an ionic strength of 0.10. From pH 5 to 7, the rate of the exchange reaction
- Margerum, Dale W.,Zabin,Janes
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p. 250 - 255
(2008/10/08)
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- The rates and mechanism of substitution reactions of nickel(II) acetylacetonato complexes
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Rates of some substitution reactions of nickel(II) acetylacetonato complexes in aqueous solution at 25° have been measured using a stopped-flow technique. Hydrolysis of the bis complex occurs in two steps, the second about 200 times slower than the first. Rates of hydrolysis depend on (H+), suggesting that hydrogen ion traps a half-bonded chelate, causing the reaction to go to completion. When nucleophilic reagents are added, rates of hydrolysis are increased. This effect is attributed to rapid replacement of a water molecule in the first coordination sphere of the nickel by the anion prior to hydrolysis, and not to a direct nucleophilic attack on the metal. The results are rather similar to those found earlier for Pd(acac)2, with which they are compared.
- Pearson, Ralph G.,Moore, John W.
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p. 1523 - 1528
(2008/10/08)
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- The effect of acetate ion on the reaction between copper(II) and the ethylenediaminetetraacetatonickelate(II) ion
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The kinetics of the substitution reaction between the mono- and diacetate complexes of copper(II) and the ethylenediaminetetraacetatonickelate(II) ion have been studied at several pH values at an ionic strength of 1.25 maintained with sodium perchlorate. The temperature dependence of both forward and reverse rates has been determined. In the forward reaction, the formation of acetate complexes of copper(II) causes a decrease in reaction rate, whereas in the reverse reaction, an increase in reaction rate is observed. These differences are compared to similar exchange systems and discussed in terms of proposed dinuclear reaction intermediates and the rates of loss of water from the hydrated and complexed ions.
- Bydalek
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p. 232 - 235
(2007/12/05)
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- Multidentate ligand kinetics. V. Copper(II) and cyclohexylenediaminetetraacetatonickelate(II)
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The kinetics of the substitution reaction between the hydrated copper(II) ion and the cyclohexylenediaminetetraacetatonickelate(II) ion are studied from pH 1.5 to 3.5. In contrast to the dominant role of copper ion attack in the similar reaction with ethylenediaminetetraacetatonickelate(II), there is no copper ion attack of cyclohexylenediaminetetraacetatonickelate(II). The reaction is first order in the complex and independent of copper concentration but it is highly pH dependent. The acid dissociation rate constants are resolved. The absence of any copper dependence is attributed to the inability of the ion to form dinuclear iminodiacetate intermediates because of hindered rotation and steric blocking due to the hydrocarbon ring. The proposed mechanism indicates that nickel-nitrogen bond dissociation must be a rate-determining step in these multidentate ligand exchange reactions.
- Margerum,Bydalek
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p. 683 - 688
(2008/10/08)
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