Chelating agents metal complexation

Some ligands have more than one atom with an unshared pair of electrons and hence can form more than one bond with a central metal atom. Ligands of this type are referred to as chelating agents the complexes formed are referred to as chelates (from the Greek chela, crab s claw). Two of the most common chelating agents are the oxalate anion (abbreviated ox) and the ethylenediamine molecule (abbreviated en), whose Lewis structures are... 

For the same reason, chelating agents that complex metal ions needed for the action of deoxyribonucleases are used to protect DNA. Care is necessary to avoid... 

Metal—/ vivo site + Chelating agent -+ Metal—Chelating agent complex... 

Several chelating or metal-complexing polymers were reported in Volume 1 of the series (p. 362). There is still considerable activity in this area and polystyrene remains one of the most widely-used supports. Selective chelate-forming ion-exchange resins were prepared from polystyrene by nitration followed by reduction, diazotization then coupling with aromatic amines and derivatives of phenol. Poly(styryl-l,8-naphthyridine) (7) also functions as a chelating agent with Cu ,... 

Sequestrants (chelating agents) form complexes with metal ions, thus preventing oxidation, undesirable discoloration and turbidity (calcium disodium ethylenediaminetetraacetate, E386 and its salts and phosphates, E450-E452). 

Liquid-liquid extractions using ammonium pyrrolidine dithiocarbamate (APDC) as a metal chelating agent are commonly encountered in the analysis of metal ions in aqueous samples. The sample and APDC are mixed together, and the resulting metal-ligand complexes are extracted into methyl isobutyl ketone before analysis. 

Certain compounds, known as chelating agents (qv), react synergisticaHy with many antioxidants. It is beheved that these compounds improve the functional abiUties of antioxidants by complexing the metal ions that often initiate free-radical formation. Citric acid and ethylenediaminetetraacetic acid [60-00-4] (EDTA), C2QH2gN20g, are the most common chelating agents used (22). 

In the most common method for chemiluminescent immunoassay (GLIA), after the immunological reaction and any necessary separation steps, the labeled compounds or complexes react with an oxidizer, eg, hydrogen peroxide, and an enzyme, eg, peroxidase, or a chelating agent such as hemin or metal... 

Platinum-group metals (qv) form complexes with chelating polymers with various 8-mercaptoquinoline [491-33-8] derivatives (83) (see Chelating agents). Hydroxy-substituted quinolines have been incorporated in phenol—formaldehyde resins (84). Stannic chloride catalyzes the condensation of bis(chloromethyl)benzene with quinoline (85). 

Metal Deactivation. Compounds capable of forming coordination complexes with metal ions are needed for this purpose. A chelating agent such as ethylene-diaminetetraacetic acid (EDTA) is a good example. 

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