Octahedral cobalt(III) complexes of the chloropentammine type. Part VI. Kinetic evidence for the ion-pair mechanism of base hydrolysis of cobalt(III) complexes in aqueous solution

1966 ◽  
pp. 1124 ◽  
Author(s):  
S. C. Chan
Keyword(s):  
Aqueous Solution ◽  
Ion Pair ◽  
Base Hydrolysis ◽  
Hydrolysis Of

Reactivity of base catalysed hydrolysis of 2-pyridinylmethylene-8-quinolinyl-Schiff base iron(II) iodide complexes: solvent effects

2013 ◽  
Vol 67 (4) ◽  
Author(s):  
Ahmad Mohamad ◽  
Mohamed Adam
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Solvent Effects ◽  
Base Hydrolysis ◽  
Iodide Ions ◽  
Ligand Structure ◽  
Solvation Parameters ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Direct Condensation

AbstractThree ligands of 2-pyridinylmethylene-8-quinolinyl (L1), methyl-2-pyridinylmethylene-8-quinolinyl (L2), and phenyl-2-pyridinylmethylene-8-quinolinyl (L3), Schiff bases were synthesised by direct condensation of 8-aminoquinoline with 2-pyridinecarboxaldehyde, 2-acetylpyridine, or 2-benzoylpyridine. They coordinated to Fe(II) ion in a 1: 2 mole ratio followed by treatment with iodide ions affording complexes with a general formula [Fe(L)2]I2·2H2O, (L = L1, L2, or L3). Spectrophotometric evaluation of the kinetics of base catalysed hydrolysis of these complex cations was carried out with an aqueous solution of NaOH in different ratios of water/methanol binary mixtures. Kinetics of the hydrolysis followed the rate law (k 2[OH−] + k 3[OH−]2)[complex]. Reactivity trends and their rate constants were compared and discussed in terms of ligand structure and solvation parameters. The methanol ratio affects the hydrolysis as a co-solvent which was analysed into initial and transition state components. The increase in the rate constant of the base hydrolysis of Fe(II) complexes, as the ratio of methanol increases, is predominantly caused by the strong effect of the organic co-solvent on the transition states.

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.

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