Complex cumulative stability constant

Hydrolysis and, more generally, complex formation equilibria may be described by cumulative stability constants, Using the Equations (3.28)-(3.31)... 

Figure 7. Cumulative stability constants for some Fe(III) complexes and solids at I = 0, plotted against the constants for corresponding Al(lll) complexes and solids. The dashed line is drawn for reference through equal log values for...

TABLE 20 Cumulative stability constants reported for the formation of mononuclear and homometallic binuclear complexes in acetonitrile solution (spectrophotometric titration of Lk or [M(L/c)3]" 10 M)... 

The constant of this equilibrium is called the overall or cumulative stability constant of the MX Y W" complex. The quantitative expression for cumulative stability constant, can be greatly simplified by removing those terms that are constant. The number of water molecules attached to each metal ion is constant. In dilute solutions, the concentration of water is effectively constant. Then, the equation written without indicating molecules of the solvent becomes ... 

It should be noted that cumulative stability constants characterize complete dissociation of the complex compound. It is clear that the equilibria, representing the... 

Table 9.1 Cumulative stability constants of Sn(ll) and Co(ll) citrate complexes used in simulations.

Table 9.4 Cumulative stability constants of Co(ll) and Mo(VI) citrate complexes.

Polarographic methods were used by Frost et al. ° to determine the cumulative stability constants (/ four ligands would be represented as Pt) of substituted thiourea derivatives with Cu(l) in acid. Values for p4 that were greater than 10 were determined for thiourea, hexahydropyrimidine-2-thione, and several other complexes with Cu(l). These very high stability coefficients in acid explain the abiiity of these iigands to prevent copper from plating onto steel in HCI at acid concentrations >1 M. 

For many purposes the cumulative stability constant (P) is required this is the product of the individual constants. If there are two individual constants, the product is designated P if there are three constants, P3. Stability constants are usually determined by potentiometric (glass electrode) titration of the ligand, in the presence and absence of the metal, and the results are processed by a set of rather complex calculations for which a computer programme can conveniently be used. 

The results suggest that the complex cyanides can be grouped into three categories depending on the cumulative formation constant and stability of the complex. 

As a conclusion, we can say that the interlayer cations have an important role in the valine sorption mechanism. The total quantity of the adsorbed valine increases in the following order calcium-montmorillonite < copper-montmorillonite < zinc-montmorillonite. This order can be explained by the cumulative effect of the affinity of cations to the layer charges (Table 2.2) and the stability constants of metal ion-valine complexes in the solution (Table 2.11). 

The stability of a complex is usually described by its stability constant, which is also known as its formation or association constant. The stability constant may refer to a stepwise or a cumulative (overall) complex-formation reaction. If ATassoc applies to the simple reaction... 

Further evidence for organometallic interactions was provided by complexation capacity measurements and pseudo stability constant determinations. Complexation capacity or the residual complexing ability of a natural water sample was determined by complexometric titration of the < 0.4-juLin filtrate with soluble copper (II) (18, 40, 44) followed by ASV measurement of free and labile copper. Plots of ASV peak current vs. the cumulative copper concentration as shown in Figure 9 were made, and the intersection of lines drawn from the intitial and final linear response regions was defined as the residual complexation capacity (43, 44,45). Complexation capacity measurements for fall 1978 are listed in Table VII. The average values for Sites 1-4 were 0.88, 0.99, 0.90, and 1.08 fiM, respectively. 

To have a reliable comparison of the relative stabilities of the different members of the series and a clear picture of the selectivity trend, the cumulative and stepwise constants obtained from the analysis of the pH-metric titrations were translated into conditional stability constants. Such constants are calculated, for every pH value, as the quotient between the sum of the complexed species and the product... 

When the chemical interactions between complexes and ligands proceed with a sufficiently high rate, it is common to treat their concentrations as close to equilibrium ones. Assumptions of such kind have been of frequent use and can be found in different problems of electrochemical kinetics. Then, the relations between concentrations might be determined by cumulative (fij) or stepwise (Kj) stability constants of complexes and protonated ligands. An expression for Pj is given in Chapter 1 stepwise equilibria, such as (3.16) and (3.17), can be characterized by... 

Cumulative constants of some ferrous and ferric complexes involving the same ligand are compared below in the order of increasing stability of the ferric ion complex. Strong (largely inner-sphere) complexes have been marked with an asterisk. 

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