scholarly journals Free-energy relationships in coordination chemistry. I. Linear relationships among equilibrium constants

1970 ◽  
Vol 48 (16) ◽  
pp. 2549-2564 ◽  
Author(s):  
E. Nieboer ◽  
W. A. E. McBryde
Keyword(s):  
Free Energy ◽  
Metal Ions ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Mutual Dependence ◽  
Linear Relationships ◽  
Stability Constants Of Complexes ◽  
Reference Ligand ◽  
Energy Relationships ◽  
Semi Empirical

After a review of previous semi-empirical free-energy relationships applying to the formation of metal complexes, the following equations are derived within a framework of logical assumptions[Formula: see text]These compare stability constants of complexes formed by a metal ion M and a ligand L with those formed by a reference metal Ms and a reference ligand Lo. The derivation of these equations reveals an inherent relationship between the constants B and C, which is formulated through an "exactness" test. The application of these relationships to stoichiometric equilibrium constants is discussed.In the testing of the foregoing equations with data for various ligand families reacting with numerous metal ions, two principal modes of behavior were noted. In one, there was a mutual dependence of B on the particular metal ions compared and of C on the particular ligands compared. In the other, all values of B and C were found to equal unity irrespective of metal ion or ligand compared. The cause of this distinction is not yet understood.

Substituent effects on intramolecular selectivity and free energy relationships in anodic and metal-ion oxidations of 5-substituted 1,2,3-trimethylbenzenes

1986 ◽  
Vol 51 (24) ◽  
pp. 4544-4548 ◽  
Author(s):  
Enrico Baciocchi ◽  
Antonella Dalla Cort ◽  
Lennart Eberson ◽  
Luigi Mandolini ◽  
Cesare Rol
Keyword(s):  
Free Energy ◽  
Metal Ion ◽  
Substituent Effects ◽  
Energy Relationships

Free-energy Relationships in Coordination Chemistry. III. A Comprehensive Index to Complex Stability

1973 ◽  
Vol 51 (15) ◽  
pp. 2512-2524 ◽  
Author(s):  
E. Nieboer ◽  
W. A. E. McBryde
Keyword(s):  
Metal Ions ◽  
Complex Stability ◽  
Ionic Charge ◽  
Class A ◽  
Comprehensive Index ◽  
Linear Relationships ◽  
Class B ◽  
Energy Relationships ◽  
Two Parameter ◽  
Numerical Index

Efforts to relate metal-complex stability constants to some property of the metal ions involved have led to the development of a correlating numerical index Q with the following characteristics: (i) Q is a two parameter quantity involving ionic charge and electronegativity, which may assume different values for a particular metal according to the type of ligand with which complexes are formed; (ii) linear relationships are obtained for plots of log KMLvs. Q for various metals and more than thirty ligands. The effect of the thermodynamic and structural properties of ligands and metal complexes on the slope and intercept in this correlation is discussed. Two new indices to class b behavior are introduced, one for metal ions and one for ligands. The index Q is shown to be related to other published indices of ionic or covalent, class a or class b, behavior of metals and ligands; the alternative ways of assigning Q may be regarded as reflecting the varying degrees of ionic or covalent character in the complexes of a given metal.

Free-energy relationships in coordination chemistry. II. Requirements for linear relationships

1970 ◽  
Vol 48 (16) ◽  
pp. 2565-2573 ◽  
Author(s):  
E. Nieboer ◽  
W. A. E. McBryde
Keyword(s):  
Free Energy ◽  
Strong Interactions ◽  
Thermodynamic Quantities ◽  
Reaction Site ◽  
Independent Variables ◽  
Linear Free Energy ◽  
Linear Relationships ◽  
In Series ◽  
Energy Relationships ◽  
Equilibrium Relationships

This paper discusses factors predisposing to linear free energy relationships among families of metal complexes. It is postulated that changes occurring at a reaction site in a test series of reactions and the corresponding changes in a reference series have their origins in the same independent variables. Linearity is seen to be favored when changes in the reaction site or in ligand substituents are small, and in the absence of strong interactions with the solvent. In addition to such considerations of a molecular sort, a number of relationships among the thermodynamic quantities ΔH0, ΔS0, and ΔG0 which have been identified as having a significant influence on rate and equilibrium relationships in series of organic reactions are discussed in terms of their effect on metal–ligand systems.

scholarly journals LINEAR FREE ENERGY RELATIONSHIPS CONCERNING REACTION RATES IN MODERATELY CONCENTRATED MINERAL ACIDS

1966 ◽  
Vol 44 (16) ◽  
pp. 1917-1931 ◽  
Author(s):  
J. F. Bunnett ◽  
Fredric P. Olsen
Keyword(s):  
Free Energy ◽  
Transition State ◽  
Reaction Rates ◽  
Mineral Acid ◽  
Linear Free Energy Relationships ◽  
Linear Free Energy ◽  
Linear Relationships ◽  
Mineral Acids ◽  
Energy Relationships ◽  
Better Than

Linear relationships exist between log kψ + H0 (for reactions of weakly basic substrates) or log kψ (for reactions of strongly basic substrates) and (H0 + log [H+]). These are linear free energy relationships. For weakly basic substrates, the correlations obtained are better than in plots of (log kψ, + H0) versus log [Formula: see text] or of log kψ versus −H0. The slopes in plots of log kψ or (log kψ + H0), as appropriate, against (H0 + log [H+]) are taken as parameter, [Formula: see text], which characterizes the response of the reaction rate to changing mineral acid concentration. Values of [Formula: see text] for reactions of strongly basic substrates reflect only relationships between protonated substrate and transition state, and may be related to reaction mechanism. [Formula: see text] values for reactions of weakly basic substrates reflect both equilibrium protonation of the substrate and transformation of protonated substrate to transition state, and are therefore less directly related to mechanism. However, the [Formula: see text] values for the two steps are additive and that for the latter step can be obtained by subtraction if the overall [Formula: see text] value and that for equilibrium protonation are known.

The stability constants of ethylenediphosphinetetraacetate complexes

1982 ◽  
Vol 47 (4) ◽  
pp. 1078-1085 ◽  
Author(s):  
Jana Podlahová ◽  
Jaroslav Podlaha
Keyword(s):  
Aqueous Solutions ◽  
Metal Ions ◽  
Stability Constants ◽  
Metal Ion ◽  
Computer Programs ◽  
Data Treatment ◽  
Relative Affinity ◽  
Stability Constants Of Complexes ◽  
Soft Metal ◽  
The Stability

The stability constants of complexes formed by the anions of ethylenediphosphinetetraacetic acid and the metal ions Cu(I), Ag(I), Ca(II), Mn(II), Fe(II), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II) and La(III) were determined by various methods (mainly potentiometry and UV-VIS spectrophotometry), followed by data treatment using standard computer programs. The type and stability of the complexes formed depend mostly on the relative affinity of the particular metal ion for the two donor groups of the ligand. Unlike EDTA, the ligand is highly selective for soft metal ions, whose complexes are very stable even in strongly acidic aqueous solutions.

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