Dimethylglyoxime, nickel complex

The formation of nickel dimethylglyoximate complex may be expressed as follows ... 

Golikand AN, Asgari M, Maragheh MG, Shahrokhian S (2006) Methanol electrooxidation on a nickel electrode modified by nickel-dimethylglyoxime complex formed by electrochemical synthesis. J Electroanal Chem 588(1) 155-160... 

Cardoso WS, Dias VLN, Costa WM, Rodrigues ID, Marques EP, Sousa AG, Boaventura J, Bezeria CWB, Song CJ, Liu HS, Zhang JJ, Marques ALB (2009) Nickel-dimethylglyoxime complex modified graphite and carbon paste electrodes preparation and catalytic activity towards methanol/ethanol oxidation. J Appl Electrochem 39(l) 55-64... 

The anode electrode-catalyst is one of the important components of the alkaline fuel cell as it helps in the electro-oxidation of fuel. It is desirable that the anode electrode-catalyst provides faster reaction kinetics and 100% oxidation of fuels to CO2 and H2O. The most widely used catalyst, without doubt, is platinum. Platinum seems to be the best choice for acidic solutions, but other metallic alloy with platinum or other metals can match its performance in alkaline medium because of the favorable fuel oxidation in alkaline medium. Different anode materials based on Pt (Prabhuram et al. 1998, Moralldn et al. 1995, Tripkivic et al. 1996), Pt-Ru (Wang et al. 2003, Manoharan et al. 2001), Co-W alloys (Shobba et al. 2002), sintered Ag/ PdO (Koscher et al. 2003), spent carbon electrodes impregnated with Fe, Fe" or Ag (Verma 2000), nickel impregnated silicate-1 (Khalil et al. 2005) and nickel dimethylglyoxime complex (Golikand et al. 2005) are some of the catalysts studied for the electro-oxidation of methanol in alkaline medium. 

Golikand, A.N., Shahrokhian, S., Asgari, M., Maragheh, M.G., Irannejad, L. and Khanchi, A. Electrocatalytic oxidation of methanol on a nickel electrode modified by nickel dimethylglyoxime complex in alkaline medium , J. Power Sources, 144 (2005) 21-27. 

Discussion. Nickel (200-400 fig) forms the red dimethylglyoxime complex in a slightly alkaline medium it is only slightly soluble in chloroform (35-50 fig Ni mL -1). The optimum pH range of extraction of the nickel complex is 7-12 in the presence of citrate. The nickel complex absorbs at 366 nm and also at 465-470 nm. 

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. 

In another procedure [522] the sample of seawater (0.5-3 litres) is filtered through a membrane-filter (pore size 0.7 xm) which is then wet-ashed. The nickel is separated from the resulting solution by extraction as the dimethylglyoxime complex and is then determined by its catalysis of the reaction of Tiron and diphenylcarbazone with hydrogen peroxide, with spectrophotometric measurement at 413 nm. Cobalt is first separated as the 2-nitroso-1-naphthol complex, and is determined by its catalysis of the oxidation of alizarin by hydrogen peroxide at pH 12.4. Sensitivities are 0.8 xg/l (nickel) and 0.04 xg/l (cobalt). 

Rampon and Cavelier [523] used atomic absorption spectrometry to determine down to 0.5 xg/l nickel in seawater. Nickel is extracted into chloroform from seawater (500 ml) at pH 9-10, as its dimethylglyoxime complex. Several extractions and a final washing of the aqueous phase with carbon tetrachloride... 

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). 

It has been mentioned that the dimethylglyoxime complexes of nickel, palladium, and platinum, and the N-methylsalicylaldimine complexes of... 

In 1971, Otsuka etal63,64, and Klein and Nixon65 simultaneously reported the formation of nickel 7r-complexes of azobenzene. The tr-bonded structure (type IV, Fig. 3) was assigned on the basis of displacement reactions and spectroscopic evidence. Treatment of (jr-Ph—N=N-Ph)Ni (PR3)2, (R = Me, Bu, Ph), with aqueous ethanol or with dimethylglyoxime in THF resulted in the reduction of the diazeno... 

A useful spot test utilizes the fact that a suspension of red nickel dimethylglyoxime in water when treated with a neutral or acetic acid solution of a palladium salt yields the yellow palladium dimethylglyoxime, which is sparingly soluble in dilute acids. The test is best performed with dimethylglyoxime paper the latter is prepared as follows. Immerse drop-reaction paper in a 1 per cent alcoholic solution of dimethylglyoxime, dry, then immerse again in a solution of 05m nickel chloride rendered barely ammoniacal. The nickel complex precipitates wash thoroughly with water, immerse in alcohol and dry. 

Separation of iron ( Fe) with cupferron complex, and nickel ( Ni) with dimethylglyoxime complex (DMG)2Ni... 

In an alkaline medium and in the presence of oxidants, nickel forms a brown-red, water-soluble dimethylglyoxime complex which is the basis of the very popular method for determining nickel. In this complex, nickel is in the IV oxidation state, and the anionic complex has the formula Ni(Dm)3" . The usual oxidants are bromine, persulphate, or iodine, but the oxidant used has no effect on the colour obtained. Since the formation of the complex is rather slow, it is advisable to wait several minutes before measuring the absorbance. The coloured solutions are unstable. It is most impoilant to add the reagents in the following sequence H2Dm, oxidant, ammonia. 

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