Organic chelate complexes with

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Formation of metal-organic chelate complexes results in stronger complexation (i.e., larger values) compared to interaction with monodentate ligands (Chapter 3). The common types of bidentate ligands are presented in Table 4.9 the chemistry of these complexes has been extensively discussed in the literature [14,47], Chapter 3 presents the most important factors in the formation of such complexes (1) the type of binding atom (2) the chelate ring size (or bite ) ... 

It is worthwhile mentioning that there are some solvents that combine good solvency power with coordinating properties. The most salient example is 1,2-dimethoxyethane (DME), which can form chelate complexes with alkali cations. This makes easier one-electron reduction of organic substances by means of alkali metals, with the formation of anion radicals and alkali cations. 

Sharp concentration gradients of other metals (e.g., Cu, Cd, and Zn) at the redoxcline in certain fjords have been shown to be largely controlled by the chelation/complexation with organic ligands. 

The reaction of palladium reagents with amines, phosphines, and other organic ligands to produce chelated complexes with Pd-C bonds is the Cyclometalation reaction (equation 7). It has been used to synthesize thousands of complexes with Pd-alkyl and Pd-aryl bonds. These complexes are beginning to be used as very stable, high turnover number catalysts and as intermediates in the synthesis of complex natural products. The scope and limitations of this reaction are detailed in Section 8. 

The speciation and chemical form of Pu in this sediment system has not been determined, but a fraction of the sediment-plutonium inventory may be in a chemical form (i.e., chelated, associated with organic matter, complexed with inorganic substances, or soluble) that is more mobile in the system than the balance of the inventory. While ingestion of sediment appears responsible for the highest levels of Pu (body burden) in fish, this mechanism apparently has not enhanced availability of Pu to biota because concentration factors for biota in WOL were relatively low compared to those observed at other study sites. Concentration factors for biota of WOL were low even though 12% of the plutonium in the water column was a soluble form (Table VI). 

Scheme 41 outlines the essence of chiral catalysis. The chiral catalysts in general work homogeneously which means that they are small molecules, mostly monomeric and contain one (mononuclear) or sometimes two (binuclear) metal atoms in a chelate complex with chiral organic ligands. Typical metals are Pd(0), Pd(II), Rh(I), Rh(II), Cu(II) which are used for essentially non-polar reactions... 

The metabolism of certain aerobic bacteria produces strong acids, which can accelerate corrosion. The best known example are bacteria of the Thiobacillus family that are able to oxidize sulfides or sulfur compounds into sulfuric acid. Certain organic acids produced by bacteria have the ability to form chelate complexes with dissolved metal ions, changing the thermodynamic conditions for corrosion (Chapter 2). In some cases the chelates may precipitate with electrolyte cations and form a film. 

A number of organic compounds, eg, acetylacetone [123-54-6] and cupferron [135-20-6] form compounds with aqueous actinide ions (IV state for reagents mentioned) that can be extracted from aqueous solution by organic solvents (12). The chelate complexes are especially noteworthy and, among these, the ones formed with diketones, such as 3-(2-thiophenoyl)-l,l,l-trifluoroacetone [326-91-0] (C4H2SCOCH2COCF2), are of importance in separation procedures for plutonium. 

Synthetic organic chelates and natural organic complexes are sometimes more effective agronomically per unit of micronuttient than inorganic forms, but the organic materials are more expensive. The chelates can be used with both orthophosphate and polyphosphate Hquids and suspensions. 

The Lo-Cat process, Hcensed by US Filter Company, and Dow/Shell s SulFerox process are additional Hquid redox processes. These processes have replaced the vanadium oxidizing agents used in the Stretford process with iron. Organic chelating compounds are used to provide water-soluble organometaHic complexes in the solution. As in the case of Stretford units, the solution is regenerated by contact with air. 

Complexes with chelating organic reagents such as salicylaldehyde and -diketonales were first prepared by N. V. Sidgwick and his students in 1925, and many more have since been characterized, Stability, as measured by equilibrium formation conslanis, is rather low and almost invariably decreases in the sequence Lj > Na > K. This situation changed drainalically in 1967 w hen C. J. Pedersen announced the synthesis of several macrocyclie polyethers which were shown to form stable complexes with... 

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