Isomerization Mechanisms of a Labile Co(II) Octahedral Complex


  • Fabrice Riblet
  • Ghenadie Novitchi
  • Lothar Helm
  • Aurélian Gulea
  • André E. Merbach



Cobalt(ii), Isomer, Labile, 19f nmr, Paramagnetic


The labile cobalt (II) complex [Co(TUF)2(Pic)2] with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (TUF) bidentate and 4-methylpyridine (Pic) monodentate ligands was studied by variable temperature (VT) 19F NMR from 184 to 312 K. In contrast to the solid state, all the isomers are present in a CD2Cl2 solution. Thermodynamic parameters (?H° and ?S°) of each isomer with reference to the trans(N)-trans(CF3)-trans isomer were obtained from the fitting of experimental mole fraction values. A kinetics investigation of the isomerization processes was performed by lineshape analysis of the spectra using the Kubo-Sack formalism. The suggested bidentate bond-rupture mechanism involves the breaking of the weakest Co–O bond (closest to the CF3 withdrawing group) with the TUF ligand.




How to Cite

F. Riblet, G. Novitchi, L. Helm, A. Gulea, A. E. Merbach, Chimia 2006, 60, 224, DOI: 10.2533/000942906777674769.