A new enantiomerization mechanism for tripodal penta-coordinate ZnII(nta) complexes. Theoretical clarification of the observed 1H NMR spectrum

Dalton Transactions Pub Date: 2006-05-08 DOI: 10.1039/B602792J

Abstract

Based on DFT calculations (RB3LYP/LANL2DZp), the unexpected single-line 1H NMR spectrum of ZnII(nta), nta = 2,2′,2″-nitrilotriacetate, can be ascribed to a non-dissociative enantiomerization process (δδδ ? λλλ) 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.

Graphical abstract: A new enantiomerization mechanism for tripodal penta-coordinate ZnII(nta) complexes. Theoretical clarification of the observed 1H NMR spectrum
Recommended Literature