| Abstract
| - The polydentate N-donor ligand 2,4,6-tris(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine (Me2-TpzT) has been used tosynthesize the new palladium derivatives Pd(R)2(Me2-TpzT), R = C6F5, 1; R = m-C6ClF4, 2. In the case of complex2, four different atropisomers have been detected at low temperature. The new complexes exhibit a rich dynamicbehavior, including three metallotropic processes (metal-hurdling, 1,4-metallotropic shifts, and an intermolecularprocess) and two processes involving restricted rotation of aromatic rings (the polyfluorophenyl groups and theuncoordinated pyrazole group adjacent to the metal fragment). The fluxional behavior has been studied by 1H and19F NMR spectroscopy using variable temperature NMR studies and 1H,1H and 19F,19F EXSY experiments. Thestudy of solutions of 2 in 1,1‘,2,2‘-tetrachloroethane-d2 gave the following order for the free energy of activation: pyrazole rotation < 1,4-metallotropic shift < intermolecular exchange < polyfluorophenyl rotation. The process ofmetal hurdling was not found in this solvent. However, in acetone-d6 such a process was detected and was foundto be of lower energy than the 1,4-metallotropic shift. In dilute acetone-d6 or 1,1‘,2,2‘-tetrachloroethane-d2 solutions,the intermolecular process was not observed. Conclusions concerning the different mechanisms have been deducedfrom the data obtained.
- The new complexes PdR2(Me2-TpzT) (Me2-TpzT = 2,4,6-tris(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine), R = C6F5, m-C6ClF4, have been synthesized. For them, five different fluxional processes have been found, including three metallotropic processes (metal hurdling, 1,4-metallotropic shifts, and an intermolecular process) and also two processes of restricted rotation of aromatic rings (the polyfluorophenyl groups and the uncoordinated pyrazole group adjacent to the metal fragment). A clear influence of the solvent in the process of metal hurding has been found.
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