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Ligand isotopic exchange kinetics of tris(acetylacetonato)chromium(III) at elevated temperatures

Journal Article · · Inorg. Chem.; (United States)
DOI:https://doi.org/10.1021/ic50168a033· OSTI ID:7326332
;

Tris(acetylacetonato)chromium(III) (Cr(acac)/sub 3/) undergoes ligand isotopic exchange with /sup 14/C-labeled acetylacetone (Hacac) in acetonitrile (AN) at greater than 140/sup 0/C without decomposition and solvolysis. McKay's exchange rate is proportional to the complex concentration, and the first-order rate constant k/sub 0/ is dependent on the concentrations of free Hacac and water (e.g., k/sub 0/ = 8.0 x 10/sup -5/ s/sup -1/ at 166.4/sup 0/C in 0.030 M Hacac and 0.068 M water in AN). Analysis of the diagrams of k/sub 0/ vs. free Hacac and water concentrations and the deuterium isotope effect suggested a plausible mechanism. In the region (Hacac) greater than 0.1 M, free Hacac seems to interact directly with the original complex to give an intermediate, in which the proton transfer from the incoming Hacac to the leaving acac gives rise to the isotopic exchange. In the region (Hacac) less than 0.03 M, the original complex appears to give a unidentate ligand spontaneously and interacts with the free Hacac to give a similar intermediate. Water molecules seem to catalyze the intramolecular proton transfer. This chromium(III) complex gives the smallest ligand isotopic exchange rate among octahedral tris(acetylacetonato) complexes ever studied.

Research Organization:
Tohoku Univ., Sendai
OSTI ID:
7326332
Journal Information:
Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 16:2; ISSN INOCA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
400203 -- Isotope Exchange & Isotope Separation-- (-1987)
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CHROMIUM COMPLEXES
COMPLEXES
DEUTERIUM
EVEN-EVEN NUCLEI
HIGH TEMPERATURE
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
ISOTOPIC EXCHANGE
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
QUANTITY RATIO
RADIOISOTOPES
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES
YEARS LIVING RADIOISOTOPES