A new enantiomerization mechanism for tripodal penta-coordinate Zn(II)(nta) complexes. Theoretical clarification of the observed 1H NMR spectrum.
Based on DFT calculations (RB3LYP/LANL2DZp), the unexpected single-line 1H NMR spectrum of Zn(II)(nta), nta = 2,2',2''-nitrilotriacetate, can be ascribed to a non-dissociative enantiomerization process (deltadeltadelta<=>lambdalambdalambda) from C3viaC3v to C3 symmetry. The energy barrier is rather low and depends to a lesser extent on the nature of the co-ligand in [Zn(nta)X]2- (X: H-, CH3- NH2-, OCH3-, F-, Cl-, Br-, I-) and [Zn(nta)Y]- (Y: NCH, CO, N2, O(CH3)2), but more so on the overall charge of the complex. The energy barrier for enantiomerization of [Zn(nta)X]2- is between 5.7 and 6.7 kcal mol-1, and for [Zn(nta)Y]- between 2.2 and 3.1 kcal mol-1.
Puchta
Ralph
R
Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058, Erlangen, Germany.
van Eikema Hommes
Nico
N
Meier
Roland
R
van Eldik
Rudi
R