Structure and dynamics of binary and ternary lanthanide(III) and actinide(III) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) complexes. Part 2, the structure and dynamics of binary and ternary complexes in the Y(III)/Eu(III) -TTA - tributylphosphate (TBP) system in chloroform as studied by NMR spectroscopy
2010 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, 10944-10952 p.Article in journal (Refereed) Published
The stoichiometric reaction mechanisms, rate constants and activation parameters for inter-and intramolecular ligand exchange reactions in the binary Y/Eu(TTA)(3)(OH2)(2)-HTTA and the ternary Y/Eu(TTA)(3)(OH2)(2)-TBP systems have been studied in chloroform using H-1 and P-31 NMR methods. Most complexes contain coordinated water that is in very fast exchange with water in the chloroform solvent. The exchange reactions involving TTA/HTTA and TBP are also fast, but can be studied at lower temperature. The rate constant and activation parameters for the intramolecular exchange between two structure isomers in Y(TTA)(3)(OH2)(2) and Y(TTA)(3)(TBP)(OH2) were determined from the line-broadening of the methine protons in coordinated TTA. The rate equations for the intermolecular exchange between coordinated TTA and free HTTA in both complexes are consistent with a two-step mechanism where the first step is a fast complex formation of HTTA, followed by a rate determining step involving proton transfer from coordinated HTTA to TTA. The rate constants for both the interand intramolecular exchange reactions are significantly smaller in the TBP system. The same is true for the activation parameters in the Y(TTA)(3)(OH2)(2)-HTTA and the ternary Y/Eu(TTA)(3)(TBP)(OH2)-HTTA systems, which are Delta H-not equal = 71.8 +/- 2.8 kJ mol(-1), Delta S-not equal = 62.4 +/- 10.3 J mol(-1) K-1 and Delta H-not equal = 38.8 +/- 0.6 kJ mol(-1), Delta S-not equal = -93.0 +/- 3.3 J mol(-1) K-1, respectively. The large difference in the activation parameters does not seem to be related to a difference in mechanism as judged by the rate equation; this point will be discussed in a following communication. The rate and mechanism for the exchange between free and coordinated TBP follows a two-step mechanism, involving the formation of Y(TTA)(3)(TBP)(2).
Place, publisher, year, edition, pages
2010. Vol. 39, no 45, 10944-10952 p.
IdentifiersURN: urn:nbn:se:kth:diva-27091DOI: 10.1039/c0dt00314jISI: 000284066100017ScopusID: 2-s2.0-78149442088OAI: oai:DiVA.org:kth-27091DiVA: diva2:376190
QC 201012102010-12-102010-12-062010-12-10Bibliographically approved