Kinetics and mechanism of aquation and formation reactions of carbonato complexes. XII. Deuterium solvent isotope effect on the rate of acid-catalyzed decarboxylation of the carbonatobis (ethylenediamine) cobalt(III) complex ion. A mechanistic reappraisal
- State Univ. of New York, Buffalo
A recent study of the acid-catalyzed decarboxylation of the carbonatotetrakis(pyridine)cobalt(III) complex ion showed there to be rate acceleration in D/sub 2/O solvent, consistent with a proton-preequilibration mechanism. This observation directly contradicts the results of a similar study made some years ago of the analogous ion, carbonatobis(ethylenediamine)cobalt(III), for which there appeared to be deceleration in D/sub 2/O solvent. A reinvestigation of the latter reaction over a much wider acidity range has now shown the earlier work to be in error. The previously proposed generalized mechanism for aquation of chelated carbonato complex ions of the form CoN/sub 4/CO/sub 3//sup +/ (N/sub 4/ identical with various tetramine ligand groupings of uni-, bi-, or quadridentate type) has thus been revised to include a proton equilibration step. An unexpected complication arises in the interpretation of the data for the bis(ethylenediamine) complex ion in the acidity range 0.1 < (H/sup +/) < 1.0. Within these limits, the pseudo-first-order rate constant for carbonato chelate ring opening, which includes a (H/sup +/) term, overtakes and exceeds the true first-order rate constant for CO/sub 2/ release. The interesting implications of this unusual first-order successive reaction system are fully explored in the context of the present study.
- OSTI ID:
- 6883883
- Journal Information:
- Inorg. Chem.; (United States), Vol. 17:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBONATES
DECARBOXYLATION
COBALT COMPLEXES
DEUTERIUM
ISOTOPE EFFECTS
PYRIDINE
REACTION KINETICS
AZINES
CARBON COMPOUNDS
CHEMICAL REACTIONS
COMPLEXES
HETEROCYCLIC COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PYRIDINES
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES
400202* - Isotope Effects
Isotope Exchange
& Isotope Separation