Binding a meridional ligand in a facial geometry: A square peg in a round hole

Abstract

The bis(pyridylimino)isoindoline (BPI) ligand is a tridentate chelate that binds to metals via a meridional coordination mode. However, when this ligand forms a complex with Re(CO)3, an almost exclusively facial moiety, the BPI ligand deforms to coordinate in a facial mode. We have investigated this deformation via structural and theoretical means, and the non-planar binding mode of the ligand bathochromically shifts the metal to ligand charge transfer (MLCT) transition.