Dimethylglyoxime copper complex

Nickel has been determined spectrophotometrically in seawater in amounts down to 0.5 xg/l as the dimethylglyoxime complex [521,522], In one procedure [521] dimethylglyoxime is added to a 750 ml sample and the pH adjusted to 9 -10. The nickel complex is extracted into chloroform. After extraction into 1M hydrochloric acid, it is oxidised with aqueous bromine, adjusted to pH 10.4, and dimethylglyoxime reagent added. It is made up to 50 ml and the extinction of the nickel complex measured at 442 nm. There is no serious interference from iron, cobalt, copper, or zinc but manganese may cause low results. 

Samples of metal complexes isolated from the final solutions were subjected to microanalysis (for carbon, hydrogen, oxygen, and sulfur). Metals were determined colorimetrically by the following methods— copper as the complex formed with sodium diethyl dithiocarbamate (6) cobalt as the nitroso-R salt complex (7) nickel as the dimethylglyoxime complex (4). 

The reversible uptake of O2 (and CO) by a copper(ii) polyoxime complex containing l,2-bis(hydroximino)trimethylene units has been reported." Stereoregularity on the structure of the polymer may impart properties which are not observed in monomeric copper(u) dimethylglyoxime complexes. 

Nickel also is deterrnined by a volumetric method employing ethylenediaminetetraacetic acid as a titrant. Inductively coupled plasma (ICP) is preferred to determine very low nickel values (see Trace AND RESIDUE ANALYSIS). The classical gravimetric method employing dimethylglyoxime to precipitate nickel as a red complex is used as a precise analytical technique (122). A colorimetric method employing dimethylglyoxime also is available. The classical method of electro deposition is a commonly employed technique to separate nickel in the presence of other metals, notably copper (qv). It is also used to estabhsh caUbration criteria for the spectrophotometric methods. X-ray diffraction often is used to identify nickel in crystalline form. 

The precipitate is soluble in free mineral acids (even as little as is liberated by reaction in neutral solution), in solutions containing more than 50 per cent of ethanol by volume, in hot water (0.6 mg per 100 mL), and in concentrated ammoniacal solutions of cobalt salts, but is insoluble in dilute ammonia solution, in solutions of ammonium salts, and in dilute acetic (ethanoic) acid-sodium acetate solutions. Large amounts of aqueous ammonia and of cobalt, zinc, or copper retard the precipitation extra reagent must be added, for these elements consume dimethylglyoxime to form various soluble compounds. Better results are obtained in the presence of cobalt, manganese, or zinc by adding sodium or ammonium acetate to precipitate the complex iron(III), aluminium, and chromium(III) must, however, be absent. 

Soon after the introduction of dimethylglyoxime as a specific reagent for nickel by Tschugaeff-Kraut-Brunck (1905-1907), Baudisch discovered a compound which precipitates copper and iron quantitatively from acid solutions.82 He appropriately named this reagent as cupferron . It is the water soluble ammonium salt of nitrosophenylhydroxylamine (5). When dissolved in chloroform, the whitish-grey copper compound gives a bright yellow solution and the brown yellow iron(III) compound a deep red solution. This behaviour reveals the inner complex character of these derivatives (6). 

Dark blue precipitate, called Turnbull s blue Deep red bivalent cation [Fe F NJJ2 formed with iron (II) salts in mineral acid solution sensitivity, 0.3 pg Red, iron (II) dimethylglyoxime nickel, cobalt, and large quantities of copper salts interfere sensitivity, 0.04 pg Red coloration due to the complex cation [Fe(C12H8N2)3]2, in slightly acidic conditions... 

Certainly a discussion of ketone derivatives would not be complete without mentioning the planarity of bis(dimethylglyoxime)nickel(II) in noncoordinating solvents. Other dimethylglyoxal derivatives such as the pyridylhydrazide form planar complexes with nickel (II) and copper(II) (19). 

The first [M Dm3(ttnFe)2](C104)2 complexes of this type were obtained [79] by the interaction of iron(II) acetate and copper, zinc, nickel, cobalt, and manganese acetates with dimethylglyoxime and 1,4,7-trimethyl-1,4,7-triazacyclononane ttn) in methanol in the presence of triethylamine (Reaction 20). In this case, a triazamacrocycle served as the protecting group in the octahedral capping nFe "03 fragment. 

Polarographic studies of formation constants of copper(ii)-salicylate complexes have been reported. An e.p.r. study of CuCl2,DH2 (DH2 = dimethylglyoxime) shows high symmetry spectra indicative of a centre of inversion which connects two molecules of complex in the unit cell. Ten new complexes of copperfn) with NN-disubstituted-2-aminoethanol N-oxide have been synthesized. ... 

However, treatment with inorganic copper was not as effective as therapy with copper complexes. A single 5 mg/kg dose of Cu(II)(dimethylglyoxime)2 increased the life-span of mice bearing Ehrlich ascites or Sarcoma 180 tumours 2- to 3-times that of non-treated controls [358]. Other copper complexes reported to have similar antitumour activities in rodents are Cu(II)(3,4,7,8,-tetramethyl-1,10-phenanthroline) [360], Cu(IIX2-keto-3-... 

Examples of applications involving preconcentration may be found in references (79-85). Modified electrodes capable of preconcentrating the analyte onto the electrode surface have been employed to enhance the analytical sensitivity and selectivity. The most common applications appear to be in the area of metal analysis. Preconcentration has been achieved on the basis of electrostatic attraction for analysis of chromium as Cr207" (78). For more selective preconcentration, however, complexation has been employed (79-81). Dimethylglyoxime has been employed for nickel determinations (81), and dithiocarbamates (79, 80, 82, 83) for copper determination. Dithiocarba-mate modified electrodes have been used for mercury analysis (84, 85). 

Cobalt and copper salts combine with dimethylglyoxime to give soluble brown complex sslts, and thus interfere when present in large proportions. 

At pH 5—6.4 in solutions containing copper(n) and dimethylglyoximate, dmg, in equivalent amounts, a tetrametic complex [Cu(Hdmg)OH]4, A, containing two hydroxy-bridged CuN units is formed. The kinetics and mechanism of oxidation of this species by peroxodisulphate have been examined. A highly coloured intermediate, B (Amax=950 nm), is formed in the reaction at pH 10.9 according to the stoicheiometry... 

The reaction of the nickel, copper, or palladium complexes M(LH)a (L= dimethylglyoxime, salicylaldoxime) with diphenylmercury and aluminium powder in refluxing toluene affords the complexes ML2Al2Ph4. Similar complexes of composition QAI2R2X2L2 (QH2=salicylaldoxime R=alkyl X=... 

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