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Rate and mechanism of ligand exchange of tris(acetylacetonato)scandium(III) in acetonitrile

Journal Article · · Inorg. Chem.; (United States)
DOI:https://doi.org/10.1021/ic00279a011· OSTI ID:5852801
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Tris(acetylaceotnato)scandium(III) undergoes ligand exchange with the enolate form of acetylacetone in CD/sub 3/CN at 30-74/degree/C. The observed first-order rate constant, obtained by the /sup 1/H NMR method, is expressed by k/sub 0/ = k/sub 1//prime/(enol) + k/sub 2//prime/ at (complex) /approx equal/ 0.05 M. (Hacac) = 0.19 /minus/ 0.58 M, and (H/sub 2/O) = 0.026-0.26 M; k/sub 1//prime/ = 52 /plus minus/ 3 M/sup /minus/1/ s/sup /minus/1/ and k/sub 2//prime/ = 1.5 /plus minus/ 0.9 s/sup /minus/1/ at 56/degree/C. No water catalysis was observed. The k/sub 2//prime/ term is minor in the concentration region. The /Delta/H/double dagger/ and /Delta/S/double dagger/ values for k/sub 1//prime/ are 36 /plus minus/ 5 kJ mol/sup /minus/1/ and /minus/105 /plus minus/ 16 J K/sup /minus/1/ mol/sup /minus/1/, respectively. The deuterium isotope effect k/sub 1//prime/(H)/k/sub 1//prime/(D) was significant (ca. 5). The I/sub a/ mechanism is assigned to the rate-determining formation of an intermediate containing a one-ended acac/sup /minus// and a unidentate Hacac in the enol form. 16 refs., 3 figs., 4 tabs.

Research Organization:
Tohoku Univ., Sendai (Japan)
OSTI ID:
5852801
Journal Information:
Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:6; ISSN INOCA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ACETYLACETONE
CHELATING AGENTS
CHEMICAL REACTIONS
DATA
DEUTERIUM
EXPERIMENTAL DATA
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KETONES
KINETICS
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
REACTION KINETICS
REAGENTS
SCANDIUM COMPOUNDS
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS