Ligand-substitutional nature of technetium(III). Rate and mechanism of ligand exchange of tris(acetylacetonato)technetium(III) in acetylacetone

Journal Article · Wed Oct 05 04:00:00 EDT 1988 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00293a037· OSTI ID:6260142

Kido, H; Hatakeyama, Y

Tris(acetylacetonato)technetium(III), /sup 99/Tc(acac)/sup 3/ undergoes ligand exchange in acetylacetone (Hacac) at 125-141/degrees/C. The rate observed by the /sup 14/C-labeling method is expressed by rate = k/sub 1/(complex) at (complex) = 0.003-0.007 M, (Hacac) = 9.7 M, and (H/sub 2/O) = 0.04-0.1 M; k/sub 1/ = 2.1 /plus minus/ 0.1 x 10/sup -4/ s/sup -1/ at 141/degrees/C. No water catalysis was observed. ..delta..H/double dagger/ and ..delta..S/double dagger/ are 119 /plus minus/ 7 kJ mol/sup -1/ and -27 /plus minus/ 18 J K/sup -1/ mol/sup -1/, respectively. The dilution with acetonitrile reduced the rate linearly with (Hacac). The deuterium isotope effect k/sub 1/(H)/k/sub -1/ (D) was modest (2.3 /plus minus/ 0.3). The I/sub a/ mechanism is assigned to the rate-determining formation of the intermediate containing a one-ended acac/sup -/ and a unidentate Hacac. The lability and the mechanism are regarded as reflecting straightforwardly the kinetic nature of Tc/sup III/ on the basis of the previously reported linear free energy relationship between the present exchange system and the ligand-substitution processes of aqua complexes for various tervalent metal ions. The lability of Tc/sup III/ with the low-spin d/sup 4/ configuration was found to be very close to that of Cr/sup III/, much lower than that of Mo/sup III/, and slightly higher than that of Ru/sup III/ and Rh/sup III/; Mo/sup III/>> Tc/sup III/ > Ru/sup III/ > Rh/sup III/. The mechanism is consistent with that previously proposed for M/sup III/(acac)/sub 3/ complexes, on the basis of an estimated ionic radius of Tc/sup III/. 24 references, 2 figures, 2 tables.

• Research Organization: Tohoku Univ., Sendai (Japan)
• OSTI ID: 6260142
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:20; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ACETYLACETONE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CHELATING AGENTS
CHEMICAL REACTIONS
COMPLEXES
DATA
DEUTERIUM
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
HOURS LIVING RADIOISOTOPES
HYDROGEN ISOTOPES
INFORMATION
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
KETONES
LABELLED COMPOUNDS
LIGANDS
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
RADIOISOTOPES
REAGENTS
STABLE ISOTOPES
TECHNETIUM 99
TECHNETIUM COMPLEXES
TECHNETIUM ISOTOPES
TRACER TECHNIQUES
TRANSITION ELEMENT COMPLEXES
YEARS LIVING RADIOISOTOPES