Williams order, Irving

Irving-Williams order The stabilities of series of complexes with different metals fall into the sequence... 

The effect of substituents on the rate of the reaction catalysed by different metal ions has also been studied Correlation with resulted in perfectly linear Hammett plots. Now the p-values for the four Lewis-acids are of comparable magnitude and do not follow the Irving-Williams order. Note tlrat the substituents have opposing effects on complexation, which is favoured by electron donating substituents, and reactivity, which is increased by electron withdrawirg substituents. The effect on the reactivity is clearly more pronounced than the effect on the complexation equilibrium. 

Willems et al. [37] used a polarographic method to study the miconazole complexes of some trace elements. Manganese, iron, cobalt, and zinc element formed miconazole complexes with different stability constants. Polarography was used for detecting stability constants. The evolution of the respective formation constants followed the natural (Irving-Williams) order. The stepwise constant of the complexes formed increased from manganese to cobalt and decreased for zinc. The results are discussed with respect to the possible mechanism of action of miconazole. 

This selectivity sequence conform to what has often been observed in soil adsorption experiments. For transition elements, the electron configuration of the ions influences the adsorption affinity. The Irving-Williams order... 

Stepwise stability constants decrease regularly in the normal manner 178), log > log K2 > log K, as may be exemplified by the values for the Ni -maltolate system, viz. 5.5, 4.3, and 2.7, respectively 179). Stability constants (log Kf) for a selection of 3-hydroxy-4-pyranonate and 3-hydroxy-4-pyridinonate complexes of some first-row transition metal 2+ cations are listed in Table IV 10,128,180—184). The values for the 3d transition metal cations conform to the long-established Irving-Williams order... 

Extraction of transition metals from low grade ores. Factor (c) (formation of a chargeless chelate complex) can be illustrated by considering the formation of complexes between 8-hydroxyquinoline (HQ) and a mixture of metal ions, say, M2+ = Fe2+, Co2+, Ni2+, and Cu2+. This is in fact the order of increasing stability constants of the complexes MQ2 (equilibrium constants /J2 for Eq. 17.14) log 2 = 15.0, 17.2, 18.7, and 23.4, respectively, in dilute solution at 20 °C. This commonly encountered sequence for complex formation by the divalent Fe, Co, Ni and Cu ions is known as the Irving-Williams order (cf. the susceptibility of Ni2+ and Cu2+ to complexing by NTA3-, noted in Sections 14.4 and 16.5). 

The order of the stability constant of the coordination compounds of divalent metal cations with various ligands falls in the general pattern known as the Irving-Williams order (15) ... 

As described above, the catalytic activity of metal ion-exchanged zeolites for aniline formation has a good correlation with electronegativity and with the formation constant of ammine complexes of metal cations. The order of the activity agrees with the Irving-Williams order. These facts give irrefutable evidence that the transition metal cations are the active centers of the reaction. 

Many studies have been carried out concerning the stability constants of humic and fulvic acid complexes.188 190,191 Stability constants vary considerably with pH and ionic strength213 and this, together with the variable nature of the ligands involved, accounts for the range of values reported for individual metal ions in the literature. However, the stabilities of divalent metal complexes generally follow the well-known Irving-Williams order Mg < Ca < Mn < Co < Zn = Ni < Cu < Hg. 

The trend is in agreement with the Irving-Williams order for the strength of complex ion formation for metal ions. That is, Ni2+ Zn2+. 

As a consequence, the selectivity of extraction of first transition series dications does not follow the Irving Williams order when these reagents are used in base metal recovery. The bis(2-ethylhexyl)ester of phosphoric acid (D2EHPA) shows [1] a preference Zn2+ > Cr21 > Mn2+ > Fe2+ > Co2+ > Ni2+ V2+ which is exploited in the recovery of zinc from primary sources. [69] M2+ ions which form tetrahedral complexes and M3+ ions which show a preference for octahedral donor sets give neutral complexes with 4 1 and 6 1 D2EHPA metal stoichiometries respectively,... 

The first-row transition metal ions have borderline hard soft properties. Therefore, there is no simple rule to predict comparative complex stabilities for a given metal ion with the different donor atoms. In contrast, the stability of complexes of these metal ions with a given ligand does follow a general trend. Thus the stability constants for complexes with NTP increase with the metal ion in the order Co + < Mn + < Zn + < Ni " " < Cu " ", which is the usual Irving-Williams order, except for the reversal of cobalt and manganese. The usual decrease in stability with increasing atomic number is observed for the complexes with metal ions of the alkaline earth series. The stabihty of the... 

The Irving-Williams order results from an enhancement of stabilities for complexes formed with Fe, Co " ", and Cu2+... 

Exceptions to the two Irving-Williams orders for inner sphere complexes occur particularly when complexes with more than four ligands or large, assymetric ligands are compared (12). Stability constant sequences for weak outer sphere complexes, such as are formed with chloride ( 1) and fluoride (16, 40), do not obey the Irving-Williams orders. 2+... 

For transition metal cations, a reasonably well-established rule on the sequence of complex stability, the Irving-Williams order, is valid. According to this rule, the stability of complexes increases in the series... 

What is the Irving-Williams order, and how and when can it be used to predict the stability of complexes Does it apply to the stabilities of complexes formed with fulvic acid, for example ... 

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