Complex formation uncharged ligand

The enhanced selectivity of the complexed transition metal cation compared to the uncomplexed aqueous form can be expressed as a gain in the stability constant of the adsorbed complex with respect to its stability constant in the solution phase (80). The complex formation reaction and corresponding stability constants of a transition metal cation M with an uncharged ligand L in both the surface (indicated by bars) and solution phase are defined as... 

Assuming unit partition of the uncharged ligand between the equilibrium and interlamellar solution allows one to determine the overall surface complex formation constant g from the... 

When a complex is formed there is an intimate chemical interaction between the ions, or between an ion and an uncharged ligand. This is in contrast to the purely electrostatic interaction which results in the formation of an ion pair. There are situations when an unambiguous assignment of a species as an ion pair or as a complex may be difficult. These matters are discussed in Sections 1.20 and 1.21. 

The determination of perchlorate, nitrate, and iodide anions is based on the formation of an ion-association pair compound. An uncharged ligand forms a stable complex with the metal ion, which further forms an ion-association pair with the inorganic anion. The ion-association pair species is then extracted into the organic phase. 1,10-phenanthroline (phen)... 

Another of the standard palladium-catalyzed C—C bond formations is the Mizoroki-Heck reaction. This reaction is based on the palladium-catalyzed coupling of olefins with aryl or vinyl halides under basic conditions [21]. The catalytic cycle that is typically proposed for this reaction is outlined in Scheme 7.7. The first step of the reaction postulated in the mechanism is an oxidative addition of R -X to a Pd(0) complex. The next step is the insertion of the alkene to the Pd complex II. In order for this to be possible, an uncharged ligand has to break away giving a neutral Pd(II) complex that will be coordinated by the olefin. The insertion of the alkene into the Pd— bond results in the C C bond-forming step to give BO. Rotation around the C—C bond and 3-hydride elimination yields the new substituted olefin and intermediate 131. Regeneration of the active catalytic species occurs by the addition of a base. 

Although there is a tendency for the alkene complexes to contain uncharged metals, a large number of complexes are known in which the metal ions are Pd2+, Fe2+, Cu+, Ag+, and Hg2 +. As we shall see, the formation of alkene complexes of these and other metals occurs as the metals catalyze certain reactions of the ligands. 

In Chapter 3 we described how an uncharged metal complex MA is formed from a metal ion central atom) through a stepwise reaction with the anion A (ligand) of a monobasic organic acid, HA, defining a stepwise formation constant k , and an overall formation constant (3 , where... 

The formation of a coordinate complex of a metal ion arises from the tendency of the ion to acquire a stable electronic configuration by filling up its vacant atomic orbitals by electrons which the ligand makes available. The coordination complex obtained may be an uncharged or a charged species. 

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