Metal: ethylene diamine complex ions

The rate of peroxide decomposition and the resultant rate of oxidation are markedly increased by the presence of ions of metals such as iron, copper, manganese, and cobalt [13]. This catalytic decomposition is based on a redox mechanism, as in Figure 15.2. Consequently, it is important to control and limit the amounts of metal impurities in raw rubber. The influence of antioxidants against these rubber poisons depends at least partially on a complex formation (chelation) of the damaging ion. In favor of this theory is the fact that simple chelating agents that have no aging-protective activity, like ethylene diamine tetracetic acid (EDTA), act as copper protectors. 

This dye fluoresces after binding Pb+2 and Ca+2 lead is considered an interferant to the determination of calcium by this approach. However, by complexing the divalent lead ion with the heavy metal chelator TPEN (N,N,N ,N -tetrakis(2-pyridylmethyl)ethylene-diamine) prior to the addition of the fluo-3, the fluorescent... 

Mn2+, D.F.P.-ase is further activated by cysteine, histidine, thiolhistidine, and serine, histamine and 2 2 -dipyridyl. Reagents reacting with metal ions, SH groups and carbonyl groups inhibit D.F.P.-ase activity. Work is proceeding on the further elucidation of such mechanisms.1 In a somewhat similar connexion attention is called to the fact that the non-enzymic hydrolysis of D.F.P. is accelerated by heavy metals and their complexes, in particular by copper chelates of ethylene diamine, o-phenanthroline, 2 2 -dipyridyl and histidine.2... 

Copolymers of methacrylic add and ethylene termed as ethylene ionomers have been used as the base polymer for binding alkali, alkaline earth and transition metal ions. Organic amines such as n-hexylamine, hexamethylene tetraamine, 2,2,6,6-tetramethyM-hydroxy piperazine, ethylene diamine and polymeric diamines such as silicone diamine, polyether diamine and polymeric diamines such as silicone diamine, polyether diamine and polyamide oligomers considerably enhance the complex formation characteristics of Zn(II) ethylene ionomers thereby enhancing the physico-chemical properties [13]. 

When the metals exist in the complexed form, it is necessary to break up the complexes and transform the metals to "free" form amenable to chemical precipitation. Metal complexes consist of a central metal ion surrounded by a group of other organic or inorganic ions or molecules. Examples of complexing molecules are ammonia, citrates, and ethylene diamine tetra acetic acid (EDTA). 

Vickery and Vickery [9] have investigated the interference by aluminium and iron in the ion-selective electrode method for the determination of fluoride in plant extracts. They demonstrated that plant ashes may contain sufficient of these two elements to seriously interfere in the determination of fluoride when using the fluoride-selective electrode. In the presence of these metals, the known additions method gives erroneous results, as did that involving the attempted formation of complexes with ethylene diamine tetraacetic acid (disodium salt) or 1,2-cyclohexylenedinitrilotetraacetic acid. 

Propyl, ethylene diamine Si-O-Si-C -CH2CH2CH2-NHCH2CH2NH2 Ion exchange Weak anion exchange phase for aqueous and biological samples incorporates a bidentate ligand to form chelate complexes useful for metal separations less polar than the propyl amine bonded phase... 

The reaction scheme in Equation 7.45 represents the complex formation reaction between a metal ion M and three equivalents of a bidentate ligand L (e.g., ethylene-diamine) to form an octahedral complex ML2. 

The treatment of complex ion equilibria in solution is analogous to the treatment of weak acids. One of the best known chelators is the well-known EDTA (ethylene diamine tetraacetic acid). The metal stability constants for EDTA are very high, which indicates strong complexes. Various other compounds are available with high metal-stability constants for agricultural or environmental uses. Some of the more important ones are DPTA (diethylene triamine pentaacetic acid), CyDTA (cyclohexane diamine tetraacetic acid), EDDA [ethylene diamine di (0-hydroxyphenyl acetic acid], or Chel-138. 

The Cu ion reacts with [OH] to form [CuOH] ", which exhibits a pH-depen-dent absorption with = 300 nm. Copper(III) complexes with NHj, ethylene-diamine and various amino acids are characterized by pulse radiolysis . The [Cu(EDTA)] (EDTA = ethylenediaminetetraacetate) and [Cu(NTA)] (NTA = nitrilotriacetate) ions are oxidized to the corresponding Chj(III) species by [OH] Cu(lII) rearranges and then metal-ligand intramolecular electron transfer yields some Cud) species. ... 

These depend upon the combination of ions other than hydrogen or hydroxide ions, to form a soluble slightly dissociated ion or compound. Ethylene diamine tetra acetic acid, mostly as the disodium salt EDTA, is a very important reagent for complex formation. The use of metal ion-indicators has highly enhanced its importance in titrimetry. The subject is discussed in section of calcium and magnesium estimation by EDTA. 

The recovery of proteins from their complexes with metals has been greatly facilitated by the introduction of ion-exchange desalting, and of the complexones such as ethylene diamine-tetra-acetic acid (EDTA), which remove the metals as non-ionised complexes. The use of specific precipitants for effecting separations covers a large field in Biochemistry, and some examples from protein chemistry are given below to illustrate the possibilities of this method. 

The most effective catalysts were found to be the 1 1 copper complexes with a,a -dipyridyl, L-histidine, o-phenanthroline, imidazole, and ethylene-diamine. Because of the apparent requirement that the metal be incompletely coordinated, it was suggested that the reactive positions of the metal are those occupied by water or hydroxide ion. Three such species have been reported by Fowkes et al. (9) from a study of aqueous equilibria involving the 1 1 dipyridyl chelate, according to the following reaction scheme ... 

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