Syntheses and structures of lanthanide complexes containing a bis(imidazolin-2-imino)pyridine pincer ligand

The Lewis acid–base reaction of 2,6-bis[1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine (TLtBu) and LnCl3 in THF leads to the corresponding neutral lanthanide complexes of type [(TLtBu)LnCl3], Ln = Y (1a), Er (1b), Lu (1c). The yttrium and lutetium complexes have been characterized by X-ray diffraction analysis. The solid state structures reveal that the bulky TLtBu ligand causes steric crowding around the lanthanide atoms by coordinating to the metal center in a tridentate fashion. In addition, remote C–H⋯Ln interactions (H⋯Ln ca. 2.7 Å) involving one of the tBu methyl groups are observed in both cases. A DFT (density functional theory) calculation on 1a was able to reproduce this interaction, which was additionally characterized by means of an H⋯Y compliance constant and by employing the AIM (atoms in molecules) theory.