Kinetic parameters for water exchange

The first experimental information on the kinetic parameters for water exchange on a tetravalent metal ion was published in 2000 for U4+ and Th4+ (265,268,271). The coordination numbers for these two complexes were determined by EXAFS to be 10 1. Based on the high coordination number (there are no complexes known with unidentate ligands and coordination numbers larger than 10) a limiting associative mechanism (A) is unlikely and a d-activated mechanism is probable. Surprisingly,... 

Table 4.1 Kinetic Parameters for Water Exchange of Divalent Transition Metal Ions, M(H20) + at 25 °C Refs. 23-25...

Table 9.9. Kinetic Parameters for Water Exchange on Aqua Complexes of Pd(II) (Ref...

Table 1 Kinetic parameters for water exchange at aquo-cations...

Table 5 Kinetic parameters for water exchange at mixed ligand complexes of nickeUji). Rate constants are values for one water molecule, at 25 0 °C...

Table 1.3 Kinetic parameters for water exchange on divalent transition metal ions...

The kinetic parameters for water exchange with the iron(III) complexes of the water-soluble porphyrins m 5o-tetrakis(A -methyl-4-pyridyl)porphine (TMpyP) and me50-tetrakis(p-sulfonatophenyl)porphine (TPPS) have been recorded they are, respectively, kx (per H2O) at 25°C = 7.8 x lO s" and 1.4 x 10 s- A// = 13.8 and 13.7 kcal mol" = 14.7 and 20.2 cal K" mol" The exchange rate is enhanced by a factor of 10" -10 over unsubstituted Feaq, A/f decreasing from 18 to 14 kcal mol Presumably the extra labilization produced by TPPS compared to TMpyP reflects a greater degree of charge donation to the iron. 

Solvent Exchange.—Kinetic parameters for water exchange at some d and d complexes of formula [ML5(OH2)] + are given in Table 21. A comparison of... 

In a study which included the determination of the structure and the acidity constants of the seven-coordinate complex aqua(o-phenylenediamine-JV,AT,A, iV -tetraacetato)ferrate(III), the temperature- and pressure-dependent kinetic parameters for water exchange were determined by ONMR line broadening to be )fc(298.2 K) = 1.2 0.2x 10 s", =26 + 3 kJ mol-, ... 

With Co +, as with Ni +, the agreement between the acetonitrile-exchange data obtained in two independent studies (Table 3) is not good. West and Lincoln point out that the kinetic parameters for the exchange of acetonitrile on bivalent metal ions exhibit trends in which hex. decreases and increases from Mn + to Ni +. Similar trends are observed for solvent exchange on these metal ions in ammonia, methanol, and water, suggesting a similar exchange mechanism in all four solvents. The observed trend in is that... 

Direct kinetic studies of water exchange on [Pd(H20)4]2+ and [Pt(H20)4]2+, the parameters for which appear in Table XIV (267-274), were first reported well after the chemistry outlined in the preceding paragraph had become established. Solvent and ligand exchange on... 

Kinetic Parameters for Fe /Fe Self-Exchange in Water at 298K. 

In another investigation,425 the exchange between [Ce(edta)aq] and hydrated Pb2+, Ni2+ or Co2+ ions again show reaction by dissociation of protonated [Ce(Hedta)aq] as well as by the direct attack of metal ions on [Ce(edta)aq] or [Ce(Hedta)aq]. The kinetic parameters for the Ni2+ or Co2+ ions could be related to the relatively slow (k - 2.6 x 106s 1 for Co2+ and 3.4 x 104 s-1 for Ni2+) water exchange reactions of these ions. The direct attack was interpreted in terms of an intermediate in which one of the carboxylate groups was coordinated to the incoming ion rather than to Ce3+. These reactions were followed by spectrophotometry at 280 nm, where the absorbance of Ce3+aq is much lower than the edta complex. 

Kinetic Parameters for Bridge-Formation and Water-Exchange Reactions of Ammine Complexes at 25°C in 1.0 A/(Na,H)CI04 ... 

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