Dimethylglyoxime ion

Spectrophotometric methods may often be applied directly to the solvent extract utilising the absorption of the extracted species in the ultraviolet or visible region. A typical example is the extraction and determination of nickel as dimethylglyoximate in chloroform by measuring the absorption of the complex at 366 nm. Direct measurement of absorbance may also be made with appropriate ion association complexes, e.g. the ferroin anionic detergent system, but improved results can sometimes be obtained by developing a chelate complex after extraction. An example is the extraction of uranyl nitrate from nitric acid into tributyl phosphate and the subsequent addition of dibenzoylmethane to the solvent to form a soluble coloured chelate. 

If the BF2 groups in Ni(dmg-BF2)2 are substituted by BPh2 units (122), the complex also adopts the saddle-shaped conformation of type D (Fig. 32), in which the two dimethylglyoxime fragments are bent down from the N4 plane with a dihedral angle of about 27° between the two least-squares planes of the dioxime units. The coordination geometry around the nickel ion is distorted square-pyramidal, but there are no intermolecular Ni Ni interactions [167]. 

Concentration of an ethanolic solution of dimethylglyoxime, cobalt(n) chloride and benzotriazole results in deposition of crystalline complex 68. The product is stable at room temperature however, it slowly decomposes upon heating. Thermal analysis reveals that the compound releases first the chlorine atom and 50% of the benzotriazole content to form a new complex that is stable to 225 °C. Probably in this new form, the benzotriazole moiety coordinates two cobalt ions simultaneously. Further heating to 350 °C removes the benzotriazolyl moieties completely <2003JPY699>. The first step of decomposition can be summarized as follows ... 

The /s.min of 12.9 eV of neutral acetoxime implies that it should also act as a base, somewhat weaker than pyridine. Indeed an important application, especially of the double oxime dimethylglyoxime (12), is in chelating metal ions. ... 

We start with butane-2,3-dione dioxime, more commonly known as dimethylglyoxime (dmg). It is a classic reagent for the analysis of NP, the green aqueous solution of metal ions transforming into a vibrantly red precipitate of Ni(dmg)2 complex it is one of the stars of the show in Ponikvar and Liebman s analytical chemistry chapter in the current volume. Here the stereochemistry is well-established and well-known—both OH groups are found on the same side as their adjacent CH3 group on the butanedione backbone. There have been several measurements of the enthalpy of formation of this species for which we take the one associated with this inorganic analytical chemistry application, i.e. with diverse metal complexes and chelates . 

Metal ions, especially transition metal ions, form coloured complexes with chelating ligands that are the basis of the analytical methods and indicators for these ions that have been used for many decades. " The term metallochromism has been apphed to this phenomenon, and hence metallochromic indicators. Typical bidentate ligands are dimethylglyoxime, 1,2-dihydoxybenzenes and 1-hydroxyanthraquinones, 8-... 

The construction and behavior of a mixed binder carbon paste electrode containing dimethylglyoxime have been described [79]. Such an electrode was used for CSV determination of mercury(II) and other metal ions. They were accumulated at the electrode surface during preconcentration step and later reduced from their complexes in the cathodic step. 

In square-planar or other lower symmetry these ions give rise to an S= 0 ground term, with consequent values of geff 0, and compounds of these types are found for all the members for example, Ni(dimethylglyoxime)2. Nickel(II) shows a form of spin-equilibrium associated with the stereochemistry interchanges... 

Electrography — Electrography, introduced independently by A. Glazunov and H. Fritz, is an obsolete technique for the direct electrochemical analysis of solid materials. The principle is that a solid specimen is pressed on a paper which is soaked with an electrolyte solution. By anodic oxidation of the surface of the solid specimen the reaction products (e.g., nickel(II) ions) react with a reagent in the paper (e.g., dimethylglyoxime) to give colored reaction product (red in case of nickel(II) and dimethylglyoxime). This produces a print that clearly shows the distribution of the reactive element (nickel, in our example) on the surface of the specimen. 

Some complexes are precipitates, like the bright-red precipitate formed between nickel(II) ions and dimethylglyoxime ... 

Place 0-2 ml test solution containing tin(II) ions (this may consist of the solution obtained from the Group IIB precipitate, reduced with magnesium) in a micro test-tube, acidify (if necessary) with dilute hydrochloric acid, add 0-2 ml 01m iron(III) chloride solution, followed by 0-3 ml 5 per cent tartaric acid solution (to prevent the formation of iron(III) hydroxide), 3 drops dimethylglyoxime reagent, and about 0 5 ml 2m ammonia solution. A red colouration is produced. 

This library was exposed to a solution of Ni(II) acetate or Fe(III) chloride in order to find the most efficient ligands for these ions among the synthesized compounds. The detection of the most stable complexes could easily be accomplished using classic color reactions (dimethylglyoxime for nickel and potassium rhodanide for iron). The colored resin beads were then selected under the microscope. Actually, certain structures proved to have a very high affinity for each of these ions. In the case of sufficiently dilute Ni(II)-solutions the metal... 

Figure 1 Selection of typical organic precipitating agents (commonly precipitated transition metal ions given in parentheses) (a) dimethylglyoxime (Ni +, Pd ), (b) 1-nitroso-2-naphthol (Fe +, Co +, Zr +, Pd +), (c) a-benzoin oxime ( cupron ) (Cu, Mo02, W02 ), (d) ammonium V-nitroso-V-phenyUiydroxylamine ( cup-ferron ) (Ti +, V02", Fe +, Zr +, 06 +, U +), (e) 8-hydroxyquino-line ( oxine ) (TiO"+, Fe +, 01 +, Zr +, Mo02 +, W02 +, Th +, U02 ), (f) 4-hydroxyphenylarsonic acid (Ti +, Zidfi...

Lev Aleksandrovich Chugaev Dimethylglyoximate test for nickel (first organic spot test reagent for a metal ion)... 

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