Evidence for the conjugate-base mechanism for the base hydrolysis of some cobalt(III) amine complexes

1968 ◽  
pp. 156
Author(s):  
C. K. Poon ◽  
M. L. Tobe
Keyword(s):  
Base Hydrolysis ◽  
Amine Complexes ◽  
Base Mechanism ◽  
Hydrolysis Of ◽  
Conjugate Base

Volumes of Activation for the Base Hydrolysis of [Rh(NH3)5X]2+ Complex Ions

1979 ◽  
Vol 32 (12) ◽  
pp. 2589 ◽  
Author(s):  
DA Palmer
Keyword(s):  
Partial Molar Volumes ◽  
Base Hydrolysis ◽  
Volume Data ◽  
Complex Ions ◽  
Molar Volumes ◽  
Base Mechanism ◽  
Hydrolysis Of ◽  
Conjugate Base

The pressure dependencies of the rates of base hydrolysis of [Rh(NH3)5X]2+ were measured at 313.2 K and μ1M, where X = Cl-, Br-, I- and NO3-, in the range 1-1500 bar. The respective Δν‡exp values are 19.3 � 0.9, 20.2 � 0.5, 20.4 � 0.5 and 22.3 � 0.9cm3 mol-1. The partial molar volumes of these complexes, as well as those of other relevant pentaamminerhodium(III) complexes, were also determined. The volume data are discussed in terms of the conventional dissociative conjugate base mechanism. The Δν‡exp for the aquation of [Rh(NH3)5NO3]2+ was found to be -6.9 � 0.4cm3 mol-1 at 313.2K, [H+] 0.005M and μ0.1 M. An I mechanism is favoured for this process.

Octahedral cobalt(III) complexes of the chloropentammine type. XVIII. Hydrolysis of some Chloroanilinebis(ethylenediamine)cobalt(III) complexes, and a rationalization for the conjugate-base and ion-pair mechanisms

1969 ◽  
Vol 22 (9) ◽  
pp. 1851 ◽  
Author(s):  
SC Chan ◽  
OW Lau
Keyword(s):  
Chloride Ion ◽  
Ion Pair ◽  
Base Hydrolysis ◽  
Methyl Substituent ◽  
Substituted Anilines ◽  
First Order ◽  
Base Mechanism ◽  
Higher Temperature ◽  
Hydrolysis Of ◽  
Conjugate Base

The kinetics for the appearance of chloride ion from aqueous solutions of the cis-chloroanilinebis(ethylenediamine)cobalt(III) cation are determined over the pH ranges of 2-3 at 40.0� and of 8-9 at 0�. By using self-buffered mixtures, the rate constants for the reaction are also measured at 40.0� as a function of the concentration of complex or of free aniline. The results are discussed in terms of the conjugate- base mechanism. A rationalization of this mechanism and the ion-pair mechanism is proposed to incorporate the base hydrolysis of other previously investigated systems where the complexes are decidedly much less acidic. At a higher temperature (65.0�), both chloride ion and aniline are liberated at similar rates, and the process is treated as parallel first-order reactions. By using complexes with meta- and para-substituted anilines, the effect of the methyl substituent on reactivity is studied.

Base hydrolysis of trans-Halogenoamminebis(dimethylglyoximato) (III). Complexes

1969 ◽  
Vol 22 (12) ◽  
pp. 2569 ◽  
Author(s):  
SC Chan ◽  
PY Leung
Keyword(s):  
Equilibrium Constants ◽  
Base Hydrolysis ◽  
Hydroxide Ion ◽  
First Order ◽  
Rate Determining Step ◽  
Rapid Formation ◽  
Pseudo First Order ◽  
Conjugate Bases ◽  
Hydrolysis Of ◽  
Conjugate Base

The disappearance of trans-[Co(LH)2(NH3)X] (LH = dimethylglyoximate ion, X = chloride or bromide) has been studied in aqueous solutions over a range of alkali concentrations at various temperatures. The kinetics were done with excess of hydroxide ion at a constant ionic strength so that pseudo first-order rate constants were obtained in all the runs. The results were interpreted in terms of the rapid formation of a pre- equilibrium species which then reacts in a rate-determining step to give products. The relatively large equilibrium constants support a conjugate-base pre-equilibrium, in which the proton is lost from oxygen, while the relatively low reactivities of the conjugate-bases are consistent with the absence of electropositive electromeric effects. The similarity in the reactivities of the chloro and the bromo conjugate-bases suggests the possibility of an SN2CB mechanism.

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