Chelating function

Ion Removal and Metal Oxide Electrodes. The ethylenediamine ( )-functional silane, shown in Table 3 (No. 5), has been studied extensively as a sdylating agent on siUca gel to preconcentrate polyvalent anions and cations from dilute aqueous solutions (26,27). Numerous other chelate-functional silanes have been immobilized on siUca gel, controUed-pore glass, and fiber glass for removal of metal ions from solution (28,29). 

Heavy metals Cation Polystyrene matrix Chelating functional groups Mineral acids... 

The complexes on surface of chelate-functionalized silica often include ligands available in solution in the coordination sphere. Use of a chromophore reagent as a ligand leads to the formation of colored mixed ligand complexes (MLC). The phenomena can be used as a basis for developing test-systems for visual determination of microquantities of inorganic cations in water. 

Similar to tannins, the polycarboxylic acid group provides a chelating function that ties up metal ions. The anionic sulfonate group functionality confers both solubility and dispersing capability for multivalent cations (calcium, iron, etc.). 

The subject of the separation and purification of metals with the aid of chitosan has been reviewed by Inoue (1998) who collected data relevant to chitosans modified with chelating functional groups as well [111]. 

Internal amino64 or imino65 67 chelate functions can achieve this type of selenenyl iodide stabilisation. 2-(4,4-Dimethyl-2-oxazolinyl)benzeneselenenyl iodide66 exhibits weak iratermolecular Se- -I contacts (372.5 pm) leading to a centrosymmetric dimer with longer N -> Se bonds (213.3 pm) and shorter Se-I bonds (277.7 pm) [Figure 19(a)] compared to the strictly monomeric 4-ethyl-substituted isomer (Se-N 207.4).65 The structure is related to the dimer of the T-shaped cyano derivative [Figure 19(b)].68... 

Resins can also be prepared with chelating functional groups which show selective affinities for certain metals. Iminodiacetic acid, vinylacetylacetone, glyoxal-thiophenol and 8-hydroxy quinoline have all been used to produce these so-called chelating resins. Their selectivities are similar to those of the free reagent. 

Structure 1031 illustrates an internally base-stabilized complex, in which the stabilizing unit is part of the added metal fragment. This contrasts to the other molecules in this section where the chelating function is part of the organic group attached to E. 

For other ligands such as malonate, which contain a chelating function but have no other obvious property which would facilitate electron transfer, it seems reasonable to ascribe the rate increase to chelation of Cr+2. In any event, it is interesting to consider the rate data for these complexes in view of this possibility, and a number of such data are presented in Table II. 

A Si-29 spectrum of the same reaction is shown in Fig. 7. Figure 8 is the Si-29 spectrum of DPMS and Al(acac)3 without 1,2-EB. The degree of complexity in the spectrum in Fig. 7 was said to be inconsistant with the formation of a copolymer. The similarity of the two spectra indicate that disproportionation of silanol material has occurred with formation of polysiloxanes. Studies by Hayes 52-541 along with the C-13 and Si-29 studies were said to point to the Al(acac)3 chelate functioning as a disproportionation catalyst for the phenyl containing silanols. 

A popular ligand is based on 2-(diphenylphosphino)pyridines [96CCR (147)1]. However, it does not necessarily fulfill the chelate function. Thus, the reaction of 2-(diphenylphosphino)pyridine with NEt4[Ir4(CO)nBr] gives [Ir4(CO)10(Ph2PPy)2], where the heterocycle acts as a monodentate P... 

Pyridylphosphinoalkane ligands are typical chelate-forming compounds, 386, extremely popular in homogenous catalysis when sometimes dearomatization of one, 387, or both arms in the pincer occurs. The chelate function may combine with the bridging mode, 388. In some specific ligands P,C,C-coordination 389 is possible. 

The introduction of chelating functional groups (e.g. amino diacetate) into polymer beads yields a product with a high affinity for metal ions, but also capable of excluding large molecules and colloidal particles from the inner pores (i.e. in some situations the column can act as a size differentiation medium) (Florence, 1977). Compared with other techniques (such as dialysis, ultra-filtration and solvent extraction), chelating column separations can be claimed to be faster and simpler, with the equipment being relatively less expensive. 

In the case of aromatic diamines, the character of metal binding is determined by a mutual position of NH2 fragments on the benzene nuclei O-phenylenediamine carries out a chelating function (161), while the meta- and para-isomers of this ligand rather carry out a bridge function (162 and 163, respectively) ... 

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