Rate and mechanism of ligand exchange of tris(acetylacetonato)scandium(III) in acetonitrile
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), Vol. 27:6
- Country of Publication:
- United States
- Language:
- English
Similar Records
Ligand isotopic exchange kinetics of tris(acetylacetonato)chromium(III) at elevated temperatures
Kinetics and mechanism of the substitution of dibenzoylmethanate for acetylacetonate in UO/sub 2/(acac)/sub 2/L (L = dimethyl sulfoxide, N,N-dimethylformamide and trimethyl phosphate)
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETYLACETONE
CHEMICAL REACTIONS
SCANDIUM COMPOUNDS
DEUTERIUM
EXPERIMENTAL DATA
ISOTOPE EFFECTS
REACTION KINETICS
CHELATING AGENTS
DATA
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
KETONES
KINETICS
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
REAGENTS
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation