Formation of stable complexes with

This chargeless molecule can be extracted by ether or amyl alcohol. In addition to this a set of complex ions, such as [Fe(SCN)]2+, [Fe(SCN)2]+, [Fe(SCN)4]-, [Fe(SCN)5]2-, and [Fe(SCN)6]3 are also formed. The composition of the product in aqueous solution depends mainly on the relative amounts of iron and thiocyanate present. Phosphates, arsenates, borates, iodates, sulphates, acetates, oxalates, tartrates, citrates, and the corresponding free acid interfere due to the formation of stable complexes with iron(III) ions. 

The result of the above reaction is even more remarkable as many simple enones or enals, e.g. acrylaldehyde, do not undergo metal-catalyzed intermolecular [3 -t- 2] cycloaddition due to formation of stable complexes with the metal which prevents the coordination of a methyl-enecyclopropane reactant. ... 

Low reactivity of pyridine compared with benzene at carbon Reaction at nitrogen prevails Formation of stable complexes with electrophiles A-Nitro Heterocycles as Nitrating Agents... 

Sugars and other polyhydroxy organic compounds interfere with the reaction of molybdic acid with monomeric silica. This is believed to be due to the formation of stable complexes with the molybdic acid (80). 

Matijevi6 (51) has discussed the applicability of the DVLO theory to various inorganic sols. In the case of silica sols, the nature of the electrolyte is of major importance. Cations vary so enormously in their adsorption and formation of stable complexes with the silica surface that the theory is of little practical value. The same conclusion was reached by Webb, Bhatnagar, and Williams in regard to colloidal TiO, (52). 

We examined the influence of cio, NO, , CC, and SO/ at various concentra-tious on the equilibrium of metal-resin interaction. Figure 2-5 show that the amoimt of metal ions taken up by a given amount of copolymer depends on the nature and concentration of the electrolyte present in the solution. Generally as concentration of the electrolyte increases, the ionization decreases, number of ligands (negative ions of electrolyte) decrease in the solution which forms the complex with less number of metal ions and therefore more number of ions may available for adsorptioir Hence on increasing concentration, nptake of metal ions may be increased, which is the normal trend. But this normal trend disturbed due to the formation of stable complex with more number of metal ions with electrolyte ligands, which decrease the number of metal ions available for adsorption, hence uptake decreases. 

These two families of amines reveal four types of behavior (1) formation of stable complexes with no observable exchange, even with excess amine (Py, n-PrNHj, i-PrNH2, Et2NH, QN) (2) formation of stable complexes with rapid... 

A combination of and n.m.r. data allows the investigation of complex formation between 9-BBN and its derivatives with amines. Four types of behaviour can be identified (a) the formation of stable complexes with no observable exchange of amine (b) the formation of stable complexes, but with rapid exchange of amine with free amine (c) the formation of partially dissociated complexes, accompanied by rapid exchange and (d) a lack of interaction between the borane and the amine. There is a regular progression from (a) to (d) with increasing steric requirements of the system. 

The experimental evidence which has accumulated in recent years shows that in every system which has been rigorously investigated the polymerization of olefins by metal halides depends upon the presence of some third substance, the co-catalyst [2-8]. The function of the cocatalyst is to provide the ions which start the polymerization proper, by forming an ionogenic complex with the metal halide. In most systems the metal halide is not consumed in the course of the reaction, so that the term catalyst in its classical sense may be retained in this respect. Exceptions to this are some polymerizations involving aluminum halides in the polymerization of propene [9], and possibly of styrene and a-methyl styrene [10], these catalysts may be inactivated by the formation of stable complexes. In other cases, such as the... 

Class (3) reactions include proton-transfer reactions of solvent holes in cyclohexane and methylcyclohexane [71,74,75]. The corresponding rate constants are 10-30% of the fastest class (1) reactions. Class (4) reactions include proton-transfer reactions in trans-decalin and cis-trans decalin mixtures [77]. Proton transfer from the decalin hole to aliphatic alcohol results in the formation of a C-centered decalyl radical. The proton affinity of this radical is comparable to that of a single alcohol molecule. However, it is less than the proton affinity of an alcohol dimer. Consequently, a complex of the radical cation and alcohol monomer is relatively stable toward proton transfer when such a complex encounters a second alcohol molecule, the radical cation rapidly deprotonates. Metastable complexes with natural lifetimes between 24 nsec (2-propanol) and 90 nsec (tert-butanol) were observed in liquid cis- and tra 5-decalins at 25°C [77]. The rate of the complexation is one-half of that for class (1) reactions the overall decay rate is limited by slow proton transfer in the 1 1 complex. The rate constant of unimolecular decay is (5-10) x 10 sec for primary alcohols, bimolecular decay via proton transfer to the alcohol dimer prevails. Only for secondary and ternary alcohols is the equilibrium reached sufficiently slowly that it can be observed at 25 °C on a time scale of > 10 nsec. There is a striking similarity between the formation of alcohol complexes with the solvent holes (in decalins) and solvent anions (in sc CO2). 

Figure 4-3. Addition of a nucleophile may lead to the formation of stable species with an increased co-ordination number. This may involve neutral acceptors or charged metal complexes.

Crown ethers selectively complex various alkali metal cations and can be thus used as model systems to study interactions between a macrocycle-bound cation and the 7r-system of a sidearm arene. Alkali-metal cation-7i interactions have recently received considerable attention because of the biological importance [88, 89, 175]. These studies have focused on Na+ and K+ interacting with benzene, phenol, and indole, which are the side chain arenes of phenylalanine, tyrosine, and tryptophan, respectively. Recent work [177-180] has demonstrated the formation of stable complexes between, for example, K+... 

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