Water-exchange rate constant

Fig. 1. Mean lifetimes of a single water molecule in the first coordination sphere of a given metal ion, th2o> and the corresponding water exchange rate constants, h2o- The tall bars indicate directly determined values, and the short bars indicate values deduced from ligand substitution studies. References to the plotted values appear in the text.

Fig. 13. Absolute partial molar volumes, Vab8°, of [Ln(H20) P in aqueous LnCl3 solutions (301) (closed circles), compared with the calculated Vabs° values (4, 42) for [Ln(H20)8]3+ and [Ln(H20)9]3 indicated by the upper and lower solid curves, respectively. Interchange rate constants, kj (298 K) (310), for the substitution of S042 on [Ln(H20) ]3+ are shown as open squares, and water exchange rate constants, fcn2o (298 K) (311, 312), for [Ln(H20)8]3+ are shown as open circles. 

Since it has been reported that in the inner-sphere SOD catal5rtic pathway (Scheme 5) the water-exchange process is the rate-limiting one, the inner-sphere catalytic rate constants is were correlated with the water-exchange rate constants on [Mn(H20)6l (22,31). However, it seems that it is not possible to draw a direct correlation between these rate constants. Firstly, is (which is pH independent) according to the observed rate law for dismutation of superoxide (V — —d[02 ]/ d = [Mn][02 ] H[H+]+ ind>, ind 2kis, ku = 2kos/KJ has the unit... 

Table 4.9 Water Exchange Rate Constants for a Number of Nickel-(II) Complexes at 25 °C. Refs. 21 and 40.

In Eq. (5.25) H2O represents a water molecule initially present outside the coordination sphere of the metal ion, which, as a result of the exchange, has entered the first coordination sphere. It follows that the degree of kinetic reactivity of aquometal ions with complexing agents parallels their kinetic lability toward water exchange. Moreover, since the water exchange rate constants of most metal ions are known, predictions on the rate of complex formation of aquometal ions can be made. 

Water exchange rate constants measured by oxygen-17 NMR... 

The only water exchange rate constants measured on square-planar aqua ions are on [Pd(H20)4 (84) and [Pt(H20)4] (29). The lability of these... 

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