Mechanism of Substitution Reactions of Complex Ions. IX. Contribution of Inductive Effects to the Rates of Acid and Base Hydrolysis of Cobalt(III) Complexes1,2

1956 ◽  
Vol 78 (12) ◽  
pp. 2676-2678 ◽  
Author(s):  
Fred Basolo ◽  
John G. Bergmann ◽  
Robert E. Meeker ◽  
Ralph G. Pearson
Keyword(s):  
Base Hydrolysis ◽  
Complex Ions ◽  
Substitution Reactions ◽  
Inductive Effects ◽  
Acid And Base ◽  
Hydrolysis Of

Substitution reactions at octahedral centers. IV. Acid and base hydrolysis of chloropentakis(alkylamine)chromium(III) ions

1969 ◽  
Vol 47 (12) ◽  
pp. 2257-2262 ◽  
Author(s):  
M. Parris ◽  
W. J. Wallace
Keyword(s):  
Base Hydrolysis ◽  
Kcal Mole ◽  
Substitution Reactions ◽  
Hydroxide Ion ◽  
Rate Determining Step ◽  
Acid And Base ◽  
Ph Dependent ◽  
Pattern Of Variation ◽  
Hydrolysis Of ◽  
Independent Reaction

The compounds [Cr(RNH2)5Cl](ClO4)2, where R = H, CH3, C2H5, n-C3H7, and n-C4H9, have been prepared and the replacement of chloride by either water or hydroxide ion subjected to kinetic examination. Below about pH 7 the reaction was acid independent, and ΔHA* was 22.4 kcal mole−1 when ammonia was the inert ligand compared with about 26.4 kcal mole−1 when the inert ligand was a primary amine. The corresponding ΔSA* values increased continuously with R from H to n-C4H9. At higher pH the rate became inversely dependent upon the acidity of the solution, and ΔHB* decreased from 26.7 kcal mole−1 for ammonia as the inert ligand to 25.4 kcal mole−1 for an amine as the inert ligand. For the pH dependent reaction the values obtained for ΔSB* were much larger than for the pH independent reaction but the pattern of variation as the inert ligands were changed was quite similar in the two cases. The great similarity in the trends of ΔS* values for the acid and base hydrolysis reactions has been interpreted in terms of a rate-determining step that is primarily dissociative in both cases.

Phosphato complexes of cobalt(III). I. General structural and hydrolytic properties

1968 ◽  
Vol 21 (1) ◽  
pp. 37 ◽  
Author(s):  
SF Lincoln ◽  
DR Stranks
Keyword(s):  
Infrared Spectra ◽  
Base Hydrolysis ◽  
Alkaline Media ◽  
Bond Rupture ◽  
Acidity Constant ◽  
Acidity Constants ◽  
Acid And Base ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Tracer Experiments

Phosphorus-32 tracer experiments have demonstrated that the phosphato ligand in [Co en2PO4]0 [Co(NH3)4PO4]O, [CO(NH3)4OH2HPO4]+, and [Co en2OH2.HPO4]+ undergoes slow substitution in acid and alkaline media at 40-60� and that a reversible hydrolysis equilibrium is established from pH 3 to 11. Outside this pH range, acid and base hydrolysis of all these phosphato complexes to diaquo or dihydroxo complexes is complete. The infrared spectra of [Co en2PO4]0 and [Co(NH3)4PO4]0 are consistent with a bidentate phosphato structure and with a monodentate phosphato ligand in CO(NH3)5PO4 and probably [Co(NH3)4OH2HPO4]+I-. The bidentate and monodentate complexes may be rapidly and reversibly interconverted but significant concentrations of the bidentate complexes only persist in the range pH 5.5-7.5. P.m.r, studies have established the predominantly cis configuration of the aquophosphato complexes. These complexes exhibit four acidity constants, one due to the aquo ligand, and three due to the monodentate phosphato ligand. The bidentate [Co en2PO4]0 exhibits a single acidity constant above pH 2. The aquophosphato complexes undergo both acid and base hydrolysis entirely by Co-O bond rupture. Acid hydrolysis of [Co en2PO4]0 also proceeds entirely by Co-O bond rupture but at pH 6.8 and in 0.25M NaOH hydrolysis proceeds by 60-65% Co-O bond rupture and by 30-35% P-O bond rupture.

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