Ligand formation

Conditional Metal—Ligand Formation Constants Recognizing EDTA s acid-base properties is important. The formation constant for CdY in equation 9.11 assumes that EDTA is present as Y . If we restrict the pH to levels greater than 12, then equation 9.11 provides an adequate description of the formation of CdY . for pH levels less than 12, however, K overestimates the stability of the CdY complex. 

Scheme 5.2-2 Different potential routes for in situ ligand formation from an imidazolium...

One of the characteristics of complexation equilibria is that, in the presence of excess concentration of a complexing ligand, formation of a complex often reduces the concentration of a free metal cation essentially to zero. This is another application of the common-ion effect discussed in the previous section. Example treats a situation of this sort. 

The initial site of protonation in these reactions has not been unambiguously determined. Alkyl ligand formation by protonation at the metal followed by a rapid 1,2-proton shift to the alkylidene ligand is equally as plausible as direct protonation at Ctt. As the metal electron density... 

The possibility of adjusting acidity/coordination properties opens up a wide range of possible interactions between the ionic liquid solvent and the dissolved transition metal complex. Depending on the acidity/coordination properties of the anion and on the reactivity of the cation (the possibility of carbene ligand formation from 1,3-dialkylimidazolium salts is of particular importance here [37]), the ionic liquid can be regarded as an innocent solvent, as a ligand precursor, as a co-catalyst or as the catalyst itself. 

Depending on the acidity/coordination properties of the anion and on the reactivity of the cation (the possibility of carbene ligand formation from 1,3-di-alkylimidazolium salts is of particular importance here [49-56]), the ionic liquid... 

Hockin, L.J. and Paine, A.J. (1983). The role of 5-aminolevulinate synthetase, haem oxygenase and ligand formation in the mechanism of maintenance of cytochrome P-450 concentration in hepatocyte culture. Biochem. Pharmacol. 210 855-857. 

The electronic structure of oxidant and reductant, nature of bridging ligand, formation as well as fission of complex are the factors which can effect the rate of the inner sphere electron transfer mechanism. 

Schindler, P. W. (1990), "Co-Adsorption of Metal Ions and Organic Ligands Formation of Ternary Surface Complexes", in M. F. Jr.. Hochelia and A. F. White, Eds., Mineral-Water Interface Geochemistry, Mineralogical Soc. of America, Washington, DC, 281-307. 

Affinity liquid chromatography and chiral separations (enantiomer separations) require similar analyte properties. The solutes may have interactions through hydrogen-bonding, ligand formation, or Coulombic forces with the surface of stationary phase materials or the sites of additives however, the selectivity is controlled by the steric effects of the structures of the analyte molecules and the recognition molecules (chiral selectors). 

Several mechanisms have been postulated to account for thallium s toxicity, including ligand formation with sulfhydryl groups of enzymes and transport proteins, inhibition of cellular respiration, interaction with riboflavin and riboflavin-based cofactors, alteration of the activity of K -dependent proteins, and disruption of intracellular calcium homeostasis. ... 

Finally, a third means of ligand formation from an imidazolium cation, described by Dupont and co-workers, should be mentioned here [34]. They investigated the hydrodimerization/telomerization of 1,3-butadiene with palladium(II) compounds in [BMIM][BF4] and described the activation of the catalyst precursor complex [BMIM]2[PdCl4] by a palladium(lV) compound formed by oxidative addition of the imidazolium nitrogen atom and the alkyl group with cleavage of the C-N bond of the [BMIM] ion, resulting in bis(methyHmidazole) dichloropalladate (Scheme 5.2-5). However, this reaction was only observed in the presence of water. 

A difference plot, also called a Bjerrum plot, is an excellent means to extract metal-ligand formation constants or acid dissociation constants from titration data obtained with electrodes. We will apply the difference plot to an acid-base titration curve. 

Fig. 30. Possible mechanism for allyl ligand formation from r/2-vinyl precursors with a /3-H available.

The aromatic dihydroxylated ligands (represented by catechol, 2,3-dihydroxybenzoate, and 4,5-dihydroxynapthalene 2,7-disulfonate) stabilize the 3+ and 2+ oxidation states of manganese in alkaline media. The data for salicylate indicate that it forms a less stable Mn(III) complex than the dihydroxy ligands. Formation of the 4+ complex is precluded because the ligands are more easily oxidized than are the Mn(III) complexes. 

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