Donor-Induced Helical Inversion of 1,1′-Binaphthyl Connecting with Two Molybdenum Complexes

Abstract

An atropisomeric biaryl molecule with a given absolute configuration could present two opposite helical conformations through the rotation around C-C single bond. To the best of our knowledge, the biaryl system is the simplest helical inversion model apart from stereomutation between two enantiomers. Herein, we first report such true helical inversion phenomena of biaryl compounds. Two [Mo(VI)O(2)(L)]-type complexes, in which L is a tridentate dioxoanionic pyridine O,N,O-ligand, are coalesced on the 2,2',3,3'-positions of an (R)-1,1'-binaphthyl unit and an intramolecular dioxo bridge is formed by two Mo=O⋅⋅⋅Mo interactions. Exterior strong donors can coordinate to molybdenum to interrupt this dioxo bridge and inversions from negative to positive chirality are explicitly observed by circular dichroism spectroscopy, consistent with single-crystal X-ray diffraction analyses.