Effect of ligand environment on the mechanism of enantiomerization of BeII, ZnII, and CuII bischelate complexes

Abstract

The effect of ligand environment on the mechanism of enantiomerization of BeII, ZnII, and CuII bischelate aminovinylketonate complexes was studied by the B3LYP/6-311++G(d,p) method. Substituents at the nitrogen atom (R = H, Me, Pri) significantly affect the mechanism of enantiomerization. In the beryllium complexes, the diagonal twist mechanism is changed to the dissociation mechanism. In the zinc complexes, only the diagonal twist mechanism is realized. The barrier to reaction monotonically increases with the size of the substituent. In the copper complexes, the effect of substituents manifests itself in the change in the relative stabilities of different forms. At R = H, the square-planar form is more stable, while the tetrahedral configuration is favorable at R = Pri. For the CuII complex with R = Me, the energy difference between two forms is less than 1 kcal mol-1, which leads to stabilization of the squareplanar structure in the solid state, whereas the tetrahedral form is more stable in solution.