2022 Volume 80 Issue 5 Pages 498-505
Chiral metal complexes have been widely used as enantioselective catalysts and chiroptical materials. In recent years, “chiral-at-metal” complexes, in which the ligand is achiral but the coordination geometry is chiral, have appeared, expanding the variety of chiral metal complexes. However, functional chiral-at-metal complexes are so far limited to those with octahedral or half-sandwich geometry. Since tetrahedral chiral-at-metal complexes usually racemize instantaneously, optically pure complexes were not available, especially in solution. Here, we present the first example of a tetrahedral chiral-at-metal complex with high configurational stability and enantioselective catalytic function. In this complex, an elaborately designed tridentate ligand imparted stability against stereoinversion while leaving a labile coordination site. We have also developed a method for the asymmetric synthesis of this chiral-at-metal complex using an acidic chiral auxiliary. The emergence of tetrahedral chiral-at-metal complexes is expected to make a significant contribution to catalytic chemistry and materials science.
