Oxime chelates

The state of the art of nickel and cobalt solvent extraction in the nickel laterite industry is assessed, covering the reagents in commercial use (organophosphorus reagents, carboxylic acids, chelating oximes and amines), research developments and chemical fundamentals that result in the different approach taken with each of the reagent types. 

Other cyclometallated Pt(iv) complexes are shown below. 7Vi6 -chelating oximes form trichloroplatinum(iv) complexes 1071 and 1072. Coordination of 2-(2-thienyl)pyridine with optically active substituents forms the Pt(ii) complex with helical chirality of the two cyclometallated ligands. Oxidative addition of bromomethylpentafluoro-benzene to the complex forms the octahedral Pt(iv) complex 1073. ... 

The copper-chelating abihty of sahcylaldoxime has been used to remove copper from brine in a seawater desalination plant effluent. A carbon—sorbate bed produced by sorption of the oxime on carbon proved to be extremely effective in the continuous process (99). In another apphcation, the chelating abihty of sahcylaldoxime with iron and copper was used to stabilize bleaching powders containing inorganic peroxide salts (100). 

The extraction of metal ions depends on the chelating ability of 8-hydroxyquinoline. Modification of the stmcture can improve its properties, eg, higher solubility in organic solvents (91). The extraction of nickel, cobalt, copper, and zinc from acid sulfates has been accompHshed using 8-hydroxyquinohne in an immiscible solvent (92). In the presence of oximes, halo-substituted 8-hydroxyquinolines have been used to recover copper and zinc from aqueous solutions (93). Dilute solutions of heavy metals such as mercury, ca dmium, copper, lead, and zinc can be purified using quinoline-8-carboxyhc acid adsorbed on various substrates (94). 

An artificial metalloenzyme (26) was designed by Breslow et al. 24). It was the first example of a complete artificial enzyme, having a substrate binding cyclodextrin cavity and a Ni2+ ion-chelated nucleophilic group for catalysis. Metalloenzyme (26) behaves a real catalyst, exhibiting turnover, and enhances the rate of hydrolysis of p-nitrophenyl acetate more than 103 fold. The catalytic group of 26 is a -Ni2+ complex which itself is active toward the substrate 1, but not toward such a substrate having no metal ion affinity at a low catalyst concentration. It is appearent that the metal ion in 26 activates the oximate anion by chelation, but not the substrate directly as believed in carboxypeptidase. 

Complexes with chelating nitrogen ligands incorporating oximes and related functions 292... 

The palladium-catalyzed reaction of benzol]quinoline in the presence of PhI(OAc)2 as an oxidant in MeCN gives an 11 1 mixture of 10-acetoxy- and 10-hydroxybenzo[ ]quinolines in 86% yield (Equation (98)).135 This chelation-directed oxidation can be extended to the benzylic C-H bond of 8-methylquinoline. The inactivated sp3 C-H bonds of oximes and pyridines undergo the same palladium-catalyzed oxidation with PhI(OAc)2 (Equation (99)).1... 

During oxide lead flotation, the choice of collector is rather limited to xanthates, which are used in operating plants. Dithiophosphates and mercaptans are used as secondary collectors. This is due to the fact that natural ores contain a variety of floatable gangues, for which the anionic flotation process is not applicable. The use of chelating agents as flotation collectors for oxide lead flotation have been extensively examined [5,6], Oximes/fuel oil... 

One method for the labeling of liposomes with chelator, hexamethylpropyleneamine oxime (HMPAO) was developed by Phillips et al. (16). Lipophilic HMPAO enters the liposome where it interacts with glutathione and becomes converted to the hydrophilic form, which is trapped in the liposome. A detailed protocol for radiolabeling liposomes using Tc-HMPAO has been reported (3). In a typical experiment, 10 to 15mCi (370-555 MBq) of Tc in the form of sodium pertechnetate... 

Triangle of Cu atoms with triply bridging OH and SO groups. Oximate ligands chelate to one Cu and bridge to another yy... 

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. ... 

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