Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Stability constants pyridine derivative complexes

We can now make sensible guesses as to the order of rate constant for water replacement from coordination complexes of the metals tabulated. (With the formation of fused rings these relationships may no longer apply. Consider, for example, the slow reactions of metal ions with porphyrine derivatives (20) or with tetrasulfonated phthalocyanine, where the rate determining step in the incorporation of metal ion is the dissociation of the pyrrole N-H bond (164).) The reason for many earlier (mostly qualitative) observations on the behavior of complex ions can now be understood. The relative reaction rates of cations with the anion of thenoyltrifluoroacetone (113) and metal-aqua water exchange data from NMR studies (69) are much as expected. The rapid exchange of CN " with Hg(CN)4 2 or Zn(CN)4-2 or the very slow Hg(CN)+, Hg+2 isotopic exchange can be understood, when the dissociative rate constants are estimated. Reactions of the type M+a + L b = ML+(a "b) can be justifiably assumed rapid in the proposed mechanisms for the redox reactions of iron(III) with iodide (47) or thiosulfate (93) ions or when copper(II) reacts with cyanide ions (9). Finally relations between kinetic and thermodynamic parameters are shown by a variety of complex ions since the dissociation rate constant dominates the thermodynamic stability constant of the complex (127). A recently observed linear relation between the rate constant for dissociation of nickel complexes with a variety of pyridine bases and the acidity constant of the base arises from the constancy of the formation rate constant for these complexes (87). [Pg.58]

Calorimetry investigations of zinc ions with functionalized pyridines have been carried out in both dimethylformamide and acetonitrile. The pyridines used were pyridine, 3-methylpyridine, and 4-methylpyridine. In DMF, for all three pyridines, four- and six-coordinate species formed and their formation constants, reaction enthalpies and entropies were determined. The stability increases linearly with increasing basicity of the pyridine derivative. The formation of the 3-methylpyridine complex is enthalpically less favorable and entropically more favorable than... [Pg.1153]

Table 3 Negative logarithms of the acidity constants (eq. 3) of some monoprotonated purine nucleobase (NB) derivatives and logarithms of the stability constants (eq. 2) of the corresponding Cd(NB) and Cd(NB - H) complexes as determined by potentiometric pH titration in aqueous solution at 25°C and / = 0.5 M (entries 1 - 7) or 0.1 M (entries 8 - 10) (NaNOs), together with data for 1-methylimidazole (IMIm) or pyridine (Py) derivatives (see Figure 5) . Table 3 Negative logarithms of the acidity constants (eq. 3) of some monoprotonated purine nucleobase (NB) derivatives and logarithms of the stability constants (eq. 2) of the corresponding Cd(NB) and Cd(NB - H) complexes as determined by potentiometric pH titration in aqueous solution at 25°C and / = 0.5 M (entries 1 - 7) or 0.1 M (entries 8 - 10) (NaNOs), together with data for 1-methylimidazole (IMIm) or pyridine (Py) derivatives (see Figure 5) .
If the reactants are oppositely charged, the collision complex in (5.18) takes the form of an outer-sphere complex with discernable stability. For the outer sphere redox reaction between Co(NH3)jL"+ and Fe(CN)g, L being a series of pyridine or carboxylate derivatives, saturation kinetics are observed, with the pseudo first-order rate constant (/ obs)> Fe(II) in excess, being given by... [Pg.268]


See other pages where Stability constants pyridine derivative complexes is mentioned: [Pg.233]    [Pg.70]    [Pg.295]    [Pg.537]    [Pg.406]    [Pg.40]    [Pg.536]    [Pg.171]    [Pg.228]    [Pg.161]    [Pg.78]    [Pg.412]    [Pg.851]    [Pg.80]    [Pg.191]    [Pg.205]    [Pg.211]    [Pg.866]    [Pg.2119]    [Pg.2118]    [Pg.1512]    [Pg.532]    [Pg.329]    [Pg.104]   
See also in sourсe #XX -- [ Pg.206 , Pg.211 ]




SEARCH



Complex Stabilization

Complexation stabilization

Complexes constants

Complexes pyridine

Complexing constants

Complexity constant

Derivatives complexation

Derivatives constant

Pyridine derivatives

Pyridine derivatives complexes

Pyridines complexation

Pyridines constants

Stability complexes

Stability constant +2 complex

Stability constants

© 2024 chempedia.info