Metallic ions-triethanolamine complexes

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

A. Direct titration. The solution containing the metal ion to be determined is buffered to the desired pH (e.g. to PH = 10 with NH4-aq. NH3) and titrated directly with the standard EDTA solution. It may be necessary to prevent precipitation of the hydroxide of the metal (or a basic salt) by the addition of some auxiliary complexing agent, such as tartrate or citrate or triethanolamine. At the equivalence point the magnitude of the concentration of the metal ion being determined decreases abruptly. This is generally determined by the change in colour of a metal indicator or by amperometric, spectrophotometric, or potentiometric methods. 

Auxiliary complexing agents such as NH3, tartrate, citrate, or triethanolamine may be employed to prevent metal ion from precipitating in the absence of EDTA. For example, Pb2+ is titrated in NH, buffer at pH 10 in the presence of tartrate, which complexes Pb2+ and does not allow Pb(OH)2 to precipitate. The lead-tartrate complex must be less stable than the lead-EDTA complex, or the titration would not be feasible. 

Irradiation of alcohol solutions of Mn(acac)20C0Cp3 and Mn(acac)3 leads to formation of the bis(acac) complex of Mn". E.s.r. examination revealed that the products arise by reduction of the central metal ion. Visible light irradiation of Mn TMPyP [TMPyP = tetrakis-(4-methylpyridyl)porphyrin] in aqueous solution containing EDTA or triethanolamine as an electron donor gives rise to the formation of Mn TMPyP. The light-induced redox cheirac-teristics of Mn °TMPyP in the presence of methyl viologen (MV ) and electron donors has also been described. ... 

Metal ions e.g., Fe, Co", Cu ) which form coloured, water-soluble complexes with HiDm interfere. However, the complexes of these metals are decomposed by EDTA, and a preliminary extraction as Ni(HDni)2 allows nickel to be isolated from Cu, Co, Fe, Cr, Al, and Mn. The presence of hydroxylamine ensures the quantitative extraction of nickel and prevents interference from Cu and Mn. In the presence of large quantities of Co and Fe the use of triethanolamine as masking agent is recommended [13]. 

Metallomicelles made up of ligand surfactants and bound metal ions have been studied extensively as artificial hydrolytic metallo-enzymes. Many such systems have become large and complex, but a study of a simple (1 1) Co(II) complex with triethanolamine showed that in the presence of CTAB or Triton X-100, it could catalyse PNPP (67) hydrolysis at pH 7 with a rate enhancement factor of 1000-fold. " ... 

The alkanolamines are used in electrolytic and chemical plating systems to improve hardness and smoothness of the coatings. Their ability to complex with many metal ions can often eliminate the use of cyanide-based electrolytes. Their use in the electrolyte baths increases bath stability and the bath s throwing power. Triethanolamine and triisopropanolamine can be used in electroless plating baths to plate copper onto metal parts. 

The effect of triethanolamine (TEA) on the conductances of solutions of alkali-metal 2,4-dinitrophenolates in THF has been ascertained the observed increase in conductivity in the presence of the TEA has been interpreted as due to formation of cation-ligand and ion pair-ligand complexes. The structures of the M -TEA complexes (1) are assumed to be similar to that found in the Na" solid-state complex the three hydroxyethyl groups of the TEA are envisioned to form a pocket of Lewis-base cations which can accept and surround the ions. ... 

Several light-induced electron transfer cycles using transition metal polypyridyl complexes that lead to catalytic fixation of CO2 or CO have been identified [69,70]. Visible light photolysis of C02-saturated aqueous acetonitrile solutions containing Ru(bpy)32+ (as photosensitizer), Co(II) ions (as the catalyst), 4,7-Me2-phenanthroline (as the ligand to complex the Co(II) in situ), triethanolamine (as donor) yields a mixture of CO and H2 (synthetic gas). The syn gas mixture is produced by simultaneous occurrence of two reduction reactions ... 

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